PHP语法如何验证验证码

上一篇文章我们讲到PHP语法如何生成验证码？，下面我们来讲讲如何PHP语法如何验证生成的验证码？

php验证验证码代码​

<?php
session_start();
 
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  $captcha = $_POST["captcha"];
  if (!empty($captcha) && strtolower($captcha) == strtolower($_SESSION["captcha"])) {
    echo "验证码输入正确！";
  } else {
    echo "验证码输入错误！"; 
  }
}
?>
<form method="post">
  <input type="text" name="captcha" placeholder="请输入验证码">
  <img src="captcha.php" onclick="this.src='captcha.php?t='+Math.random()">
  <input type="submit" value="提交">
</form>