AJAX-----03远古时期的ajax

用iframe方法实现

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <form action="3.php" method="post" target="ff">
        USER: <input type="text" name="user"> <span id="user"></span> <br> <br>
        EMAIL: <input type="text" name="emali"> <span id="emali"></span><br> <br>
        <input type="submit" value="OK">
    </form>
    <!--  width="0" height="0" frameborder="0"   加上这段代码即可隐藏掉iframe了 -->
    <iframe name="ff" ></iframe>
</body>
</html>

<?php
    /*
        业务逻辑的处理
    */
    //print_r($_POST);

    $user = $_POST['user'];
    $res = '';
    if($user == 'admin'){
        $res = 1;
    }else{
        $res = 0;
    }

?>
<script>
    /*然后在通过模版引擎将数据遍历到前端即可 如下*/
    parent.document.getElementById('user').innerHTML = 'YES';    
</script>