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;
}

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

<"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>";
}
"htmlcode">

<"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/>'; 
"htmlcode">

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····