switch

<?php
  header("Content-Type:text/html;charset=utf-8");
function alert_herf($text){
  echo'<script language="javascript">alert("'.$text.'");top.location='."'"."./login.html?a=login"."'".';</script>';
}
$type=$_GET['a'];
switch ($type) {//当变量$type的是login的时候执行,login下的内容,如果是login_api就执行login_api下的分支语句
  case 'login':
    include("./tamplate/login.html");
    break;
  case 'login_api':
    $username=$_POST['username'];
    $password=$_POST['password'];
    if (empty($username)) {
      // code...
      alert_herf("请输入用户名,再提交");
    }
    if(empty($password)){
      alert_herf("请输入密码,再提交");
    }
    if ($username == "admin" &&  $password == "123456") {
      $text= "登陆成功";
      alert_herf($text);
    }else {
      $text= "登陆失败";
      alert_herf($text);
    }
  default:
    // code...
    break;
}
?>

switch作为分支机构语句进行php的代码当中