深入理解PHP原理之Opcodes

18 Jun 08 深入理解PHP原理之Opcodes

http://www.laruence.com/2008/06/18/221.html

作者: Laruence(







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最近要给Yahoo的同事们做一个关于PHP和Apache处理请求的内部机制的讲座，刚好写了些关于Opcodes的文字，就发上来了，这个文章基于 Sara Golemon大师的《Understanding OPcode》

Opcode是一种PHP脚本编译后的中间语言，就像Java的ByteCode,或者.NET的MSL，举个例子，比如你写下了如下的PHP代码：

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"><?php</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">   <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Hello World"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">   <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$a</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">+</span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">   <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$a</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">?></span></li></ol>

PHP执行这段代码会经过如下4个步骤(确切的来说，应该是PHP的语言引擎Zend)

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">1.Scanning(Lexing) ,将PHP代码转换为语言片段(Tokens)</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">2.Parsing, 将Tokens转换成简单而有意义的表达式</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">3.Compilation, 将表达式编译成Opocdes</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">4.Execution, 顺次执行Opcodes，每次一条，从而实现PHP脚本的功能。</li></ol>

题外话:现在有的Cache比如APC,可以使得PHP缓存住Opcodes，这样，每次有请求来临的时候，就不需要重复执行前面3步，从而能大幅的提高PHP的执行速度。

那什么是Lexing? 学过编译原理的同学都应该对编译原理中的词法分析步骤有所了解，Lex就是一个词法分析的依据表。 Zend/zend_language_scanner.c会根据Zend/zend_language_scanner.l(Lex文件),来输入的 PHP代码进行词法分析，从而得到一个一个的“词”，PHP4.2开始提供了一个函数叫token_get_all,这个函数就可以讲一段PHP代码 Scanning成Tokens；

如果用这个函数处理我们开头提到的PHP代码，将会得到如下结果:

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">           <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">367</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">           <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span>  Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">316</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">2</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">3</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">315</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Hello World"</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">4</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">5</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">6</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">7</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">8</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">305</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">9</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">10</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">+</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">11</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">12</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">305</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">13</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">14</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">15</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">316</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">16</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> Array</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">370</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">            <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">1</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">        <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">    <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">17</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">]</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">=></span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li></ol>

分析这个返回结果我们可以发现，源码中的字符串，字符，空格，都会原样返回。每个源代码中的字符，都会出现在相应的顺序处。而，其他的比如标签，操作符，语句，都会被转换成一个包含俩部分的Array: Token ID (也就是在Zend内部的改Token的对应码，比如,T_ECHO,T_STRING)，和源码中的原来的内容。

接下来，就是Parsing阶段了，Parsing首先会丢弃Tokens Array中的多于的空格，然后将剩余的Tokens转换成一个一个的简单的表达式

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">1.echo a constant string</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">2.add two numbers together</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">3.store the result of the prior expression to a variable</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">4.echo a variable</li></ol>

然后就改Compilation阶段了，它会把Tokens编译成一个个op_array, 每个op_arrayd包含如下5个部分：

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">1.Opcode数字的标识，指明了每个op_array的操作类型，比如add , echo</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">2.结果       存放Opcode结果</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">3.操作数1  给Opcode的操作数</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">4.操作数2</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">5.扩展值   1个整形用来区别被重载的操作符</li></ol>

比如，我们的PHP代码会被Parsing成:

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">* ZEND_ECHO     'Hello World'</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">* ZEND_ADD       ~0 1 1</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">* ZEND_ASSIGN  !0 ~0</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">* ZEND_ECHO     !0</li></ol>

呵呵，你可能会问了，我们的$a去那里了？

恩，这个要介绍操作数了，每个操作数都是由以下俩个部分组成：

<ol style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline; list-style-type: none;"><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">a)op_type : 为IS_CONST, IS_TMP_VAR, IS_VAR, IS_UNUSED, or IS_CV</li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;"> </li><li style="margin: 0px; padding: 0px; border: 0px; font-style: inherit; font-family: inherit; vertical-align: baseline;">b)u,一个联合体，根据op_type的不同，分别用不同的类型保存了这个操作数的值(const)或者左值(var)</li></ol>

而对于var来说，每个var也不一样

IS_TMP_VAR, 顾名思义，这个是一个临时变量，保存一些op_array的结果，以便接下来的op_array使用，这种的操作数的u保存着一个指向变量表的一个句柄（整数），这种操作数一般用~开头，比如~0,表示变量表的0号未知的临时变量

IS_VAR 这种就是我们一般意义上的变量了,他们以$开头表示

IS_CV 表示ZE2.1/PHP5.1以后的编译器使用的一种cache机制，这种变量保存着被它引用的变量的地址，当一个变量第一次被引用的时候，就会被CV起来，以后对这个变量的引用就不需要再次去查找active符号表了，CV变量以！开头表示。

这么看来，我们的$a被优化成!0了。