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/>"; ?>

运行结果

hello1成功退出····hello2成功退出····hello3成功退出····hello4成功退出····hello5成功退出····hello6成功退出····hello7成功退出····hello81成功退出····我是5号出口hello61成功退出····hello6我是2号出口成功退出····