php控制结构if，switch，while，for等的代码实例

<meta http-equiv="content-type" content="text/html;charset=utf-8"/> 
<?php 
$a = 10; 
if ($a > 0) 
{ 
echo &#39;整数大于零&#39;; 
} 
echo &#39;<br/>&#39;; 
if ($a > 0) 
{ 
echo &#39;整数大于零&#39;; 
} 
else if($a < 0) 
{ 
echo &#39;整数小于零&#39;; 
} 
else 
{ 
echo &#39;整数等于零&#39;; 
} 
?>

<meta http-equiv="content-type" content="text/html;charset=utf-8"/> 
<?php 
$role = &#39;admin&#39;; 
switch ($role) 
{ 
case &#39;admin&#39; : 
echo &#39;管理员&#39;; 
break; 
case &#39;user&#39; : 
echo &#39;普通用户&#39;; 
break; 
case &#39;guest&#39; : 
echo &#39;游客&#39;; 
break; 
default : 
echo &#39;游客&#39;; 
break; 
} 
?>

<?php 
$a = 10; 
while ( $a > 0 ) 
{ 
echo $a --; 
echo &#39;<br>&#39;; 
} 
?>

<?php 
$a = 10; 
do 
{ 
echo $a --; 
echo &#39;<br/>&#39;; 
} 
while ( $a > 0 ) 
?>

<?php 
for($a = 0; $a < 10; $a++) 
{ 
echo $a; 
echo &#39;<br/>&#39;; 
} 
?>

<meta http-equiv="content-type" content="text/html;charset=utf-8"/> 
<?php 
for($a = 0; $a < 10; $a++) 
{ 
echo $a; 
echo &#39;<br/>&#39;; 
if($a ==5) 
{ 
break;//终止循环，但执行循环后面的语句 
} 
} 
echo &#39;循环结束&#39;; 
?>

<?php 
for($a = 0; $a < 10; $a++) 
{ 
echo $a; 
echo &#39;<br/>&#39;; 
if($a ==5) 
{ 
exit;//直接退出，循环后面的语句不执行 
} 
} 
echo &#39;循环结束&#39;; 
?>

<?php 
for($a = 0; $a < 10; $a++) 
{ 
echo $a; 
echo &#39;<br/>&#39;; 
if($a ==5) 
{ 
continue;//结束本次循环，继续下次循环，循环后面的语句依然执行 
} 
} 
echo &#39;循环结束&#39;; 
?>