php生成验证码

<form action="2.php" method="post">
        <input type="text" name="code">
        <img src="Control.php" alt="验证码" onclick="this.src = 'Control.php?'+Math.random()">
        <button>提交</button>
    </form>

<?php
//2.php
session_start();
if(strtolower($_POST['code']) === $_SESSION['code']) {
   
    echo 'ok';
} else {
   
    echo 'error';
}
?>

<?php
//Control.php
session_start();
include 'Captcha.php';
// //可以传递三个参数 分别是 长度 高度 验证码字符长度
$captcha = new Captcha(200,80,5);
$code = $captcha->render();
$_SESSION[