学习笔记 PHP中的流程控制书写方式有两种可选形式 [第二课]

时间：2014年2月13日

地点：刘家窑

1、下面是摘自PHP手册中的说明：

Alternative syntax for control structures

(PHP 4, PHP 5)
PHP offers an alternative syntax for some of its control structures;namely,
if, while, for, foreach, and switch. In each case, the basic form of the alternate syntax is to change the opening brace to a colon (:) and the closing brace toendif;,
endwhile;, endfor;, endforeach;, or endswitch;, respectively.

<?php if ($a == 5): ?>

A is equal to 5

<?php endif; ?>

In the above example, the HTML block "A is equal to 5" is nested within an
if statement written in the alternative syntax. The HTML block would be displayed only if$a is equal to 5.

The alternative syntax applies to else and elseif as well. The following is anif structure with
elseif and else in the alternative format:

<?php

if ($a == 5):

echo "a equals 5";

echo "...";

elseif ($a == 6):

echo "a equals 6";

echo "!!!";

else:

echo "a is neither 5 nor 6";

endif;

?>

Note:

Mixing syntaxes in the same control block is not supported.
2、下面是在linux上的实验记录：

[kevinlou@centos php]$ vim structure.php

<?php

$a = 100;

if ($a>90):

echo '$a > 90';

echo "\n";

elseif ($a > 80):

echo '$a > 80';

echo "\n";

endif;

while ($a>10):

echo $a;

echo "\n";

$a -= 10;

endwhile;

echo "\n\n";

for ($i=0;$i<$a;$i++):

echo $a;

echo "\n";

$a--;

endfor;

echo "\n\n";

$arr = array(1,2,3,4,5,6,7,8,9,0);

foreach ($arr as $key=>$val):

echo $key.'=>'.$val;

echo "\n";

endforeach;

3、下面是运行结果：

[kevinlou@centos php]$ php structure.php

$a > 90

100

90

80

70

60

50

40

30

20

10

9

8

7

6

0=>1

1=>2

2=>3

3=>4

4=>5

5=>6

6=>7

7=>8

8=>9

9=>0

4、总结和说明：

1）能够使用 冒号(:)和endxxx 语法的流程控制 只有列出的这几个 ： if while for foreach switch

2）冒号必须紧跟在关键字后面的括号后面，不能有空格

3）elseif 在这种书写方式下，只能连接在一起写，不能分开

4）两种书写方式不能混合只能使用其中一种。