采用PHP实现”服务器推”技术的聊天室
2015-02-13 14:36
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16 Apr 08 采用PHP实现”服务器推”技术的聊天室
作者: Laruence()
本文地址: http://www.laruence.com/2008/04/16/118.html
转载请注明出处
传统的B/S结构的应用程序,都是采用”客户端拉”结束来实现客户端和服务器端的数据交换。
本文将通过结合Ticks(可以参看我的另外一篇文章:关于PHP你可能不知道的-PHP的事件驱动化设计),来实现一个服务器推的PHP聊天室简单构想。
PHPer,尤其是用过set_cookie, header的,一定见过这样的提示信息:”Warning: Cannot modify header information – headers already sent by…..”, 这是因为通过HTTP协议通信,数据包会包含俩个部分,一个是Header,一个是data。一般来说,都是先Header部分,在Heaer部分指明了 Data部分的长度,然后使用\r\n\r\n来表示header部分结束,接下来是Data部分。
当我们有任何输出的时候,Header部分就发送了,这个时候,你再想header函数来改变一些Header部分的域信息,就会得到上面的提示信息。
一个简单的办法就是使用output_buffering。让它来缓存服务器的输出,不要太早将Header部分发给客户端。
那么,如果不使用output_buffering,是不是就可以实现,每当服务器有输出,就立即发送给客户端呢?
做个如下试验:
//设置php.ini中output_buffering=0 或者使用ob_end_flush()关闭缓存
<ol style="margin: 0px; padding: 0px; border: 0px; font-family: Monaco, Consolas, Courier, monospace; vertical-align: baseline; list-style-type: none; color: rgb(246, 243, 232); line-height: 18px; white-space: pre;"><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">set_time_limit</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">for</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">++)</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Now Index is :"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">.</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">sleep</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li></ol>
结果我们发现,还是要等到脚本全部执行完以后,才能一次看到所有的结果。。
为什么呢?
这是因为我们只是解决了缓存问题,但是还有一个缓冲问题,PHP会缓冲程序的输出。所以,这个时候,我们还需要调用,flush(), 来强制使得PHP将所有的程序输出发送给客户端。
<ol style="margin: 0px; padding: 0px; border: 0px; font-family: Monaco, Consolas, Courier, monospace; vertical-align: baseline; list-style-type: none; color: rgb(246, 243, 232); line-height: 18px; white-space: pre;"><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">et_time_limit</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//设置php.ini中output_buffering=0</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">ob_end_flush</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span><span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//关闭缓存</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> </li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">set_time_limit</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">for</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">0</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">++)</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">echo</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Now Index is :"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">.</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">flush</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">sleep</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li></ol>
现在是不是看到了,不断有服务器的数据显示出来(如果看不到, 可以在输出前填充相当数量的占位字符)?
有几个概念之间的关系,我这里补充以下:
在代码中使用ob_start(), 就相当于在php.ini中使用output_buffering=on一样,使用服务器缓存。
在代码中使用ob_end_flush() 就相当于在php.ini中使用output_buffering = false一样,关闭服务器缓存.
基于前面的讨论,我们就有可能使用Ticks来实现,一个无刷新,无ajax的聊天室: 页面中包含俩个iframe,一个是不断获取聊天室的聊天内容,一个包含用户发表聊天内容的form. 这样,在第一个frame的脚本中:
<ol style="margin: 0px; padding: 0px; border: 0px; font-family: Monaco, Consolas, Courier, monospace; vertical-align: baseline; list-style-type: none; color: rgb(246, 243, 232); line-height: 18px; white-space: pre;"><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">ob_end_clean</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span><span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//关闭缓存</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">set_time_limit</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">ob_implicit_flush</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span> <span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//这个语句将强制每当有输出就自动刷新,相当于在每个echo后,调用ob_flush()</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">$new_mesg</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span> NULL<span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">register_tick_function</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"getNewMesg"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">declare</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span>ticks<span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">while</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">if</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(!</span><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">is_null</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$new_mesg</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">))</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">foreach</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$new_mesg</span> <span class="sh_keyword" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(150, 203, 254);">as</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$msg</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">$msg</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$new_mesg</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">=</span> null<span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> </li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">function</span> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">getNewMesg</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">()</span><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//通过查询数据库,或者共享内存,来获取现在的聊天室大厅的内容。</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//返回一个数组,包含所有的新的聊天内容</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li></ol>
这样就实现了一个简单的使用服务器推技术的聊天室的框架。
当然,关于实时输出,还有一些其他的限制,比如在PHP5手册中讲到的:
个别web服务器程序,特别是Win32下的web服务器程序,在发送结果到浏览器之前,仍然会缓存脚本的输出,直到程序结束为止。
有些Apache的模块,比如mod_gzip,可能自己进行输出缓存,这将导致flush()函数产生的结果不会立即被发送到客户端浏览器。
甚至浏览器也会在显示之前,缓存接收到的内容。例如 Netscape 浏览器会在接受到换行或 html 标记的开头之前缓存内容,并且在接受到
标记之前,不会显示出整个表格。
一些版本的 Microsoft Internet Explorer 只有当接受到的256(甚至更多)个字节以后才开始显示该页面,所以必须发送一些额外的空格来让这些浏览器显示页面内容。
接下来,我贴一个很有趣的代码,有兴趣的同学,可以试试:
<ol style="margin: 0px; padding: 0px; border: 0px; font-family: Monaco, Consolas, Courier, monospace; vertical-align: baseline; list-style-type: none; color: rgb(246, 243, 232); line-height: 18px; white-space: pre;"><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">header</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"Content-type: multipart/x-mixed-replace;boundary=endofsection"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"--endofsection\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">$pmt</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">array</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"-"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"\\"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"|"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">"/"</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">for</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">(</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span> <span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><</span><span class="sh_number" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 115, 253);">10</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">++</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">)</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">{</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">sleep</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">);</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Content-type: text/plain\n\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Part $i "</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">.</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$pmt</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">[</span><span class="sh_variable" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(198, 197, 254);">$i</span> <span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">];</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"--endofsection\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">ob_flush</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span> <span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//强制将缓存区的内容输出</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"> <span class="sh_function" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(255, 210, 167);">flush</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">();</span> <span class="sh_comment" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(124, 124, 124);">//强制将缓冲区的内容发送给客户端</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;"><span class="sh_cbracket" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">}</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"Content-type: text/plain\n\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"The end\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li><li style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; 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);">print</span> <span class="sh_string" style="margin: 0px; padding: 0px; border: 0px; font-family: inherit; vertical-align: baseline; color: rgb(168, 255, 96);">"–endofsection–\n"</span><span class="sh_symbol" style="margin: 0px; padding: 0px; border: 0px; font-weight: inherit; font-style: inherit; font-family: inherit; vertical-align: baseline;">;</span></li></ol>
使用firefox打开,看看你看到了什么。
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