php中switch语句用法详解

本文介绍php中的switch语句的用法，它跟其他语句中的switch用法差不多的，但注意有有一个break语句。

PHP中switch语句的标准语法：

switch (expression){case label1: code to be executed if expression = label1; break; case label2: code to be executed if expression = label2; break;default: code to be executed if expression is different from both label1 and label2;}

举例：

switch($i){  case 1:    echo 1;    break;  case 2:    echo 2;    break;  default:    echo 'others';}

也可以使用switch来判断一个取值范围，或者说是在case中自定义条件。

<?phpheader("content-type:text/html;charset=utf8");$score=50;switch($score) { case $score>=90 && $score<=100:  echo "优<br>";  break; case $score>=80 && $score<90:  echo "良<br>";  break; case $score>=70 && $score<80:  echo "中<br>";  break; case $score>=60 && $score<70:  echo "及格<br>";  break; case $score>=0 && $score<60:  echo "不及格<br>";  break; default:  echo"成绩输入错误<br>";}?>

简单示例

<?php  //switch细节  //情况一：数值匹配的时候自动转换成字串  $a=1;  switch($a){   case "1":     echo 'hello1';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况二：数值匹配的时候自动转换成字符  $a=1;  switch($a){   case '1':     echo 'hello2';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况三：字符匹配的时候自动转换成数值  $a='1';  switch($a){   case 1:     echo 'hello3';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况四：字串匹配的时候自动转换成数值  $a="1";  switch($a){   case 1:     echo 'hello4';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况五：float也可以匹配  $a=1.1;  switch($a){   case 1.1:     echo 'hello5';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况六：非0是true  $a=true;  switch($a){   case 1:     echo 'hello6';     break;   case true:     echo 'hello61';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况七：能匹配boolean  $a=true;  switch($a){   case true:     echo 'hello7';     break;   case 2:     echo 'hello71';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况八：能匹配null  $a=null;  switch($a){   case 2://'' "" false 0 都能进入     echo 'hello8';     break;   case null:     echo 'hello81';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况九：退出顺序  $a=5;  switch($a){   case 1:     echo 'hello6';     break;   case 2:     echo '我是2号出口';     break;   case 5:     echo '我是5号出口';     //break;   case true:     echo 'hello61';     break;   default:     echo 'sorry none is the same!';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>';   //情况十：退出顺序  $a=50;  switch($a){   default:     echo 'sorry none is the same!';     //break;   case 50:     echo 'hello6';     //break;   case 2:     echo '我是2号出口';     break;   case 5:     echo '我是5号出口';     //break;   case 6:     echo 'hello61';     break;  }  echo '<br/>'.'成功退出····';  echo '<hr/>'; ?>