PHP Curl提交登录表单未返回预期响应问题排查

我在服务器上部署了一个用于测试Curl表单提交的基础登录页面，代码如下：

<?php
    if(isset($_POST['submit'])){
        $email = $_POST['email'];
        $password = $_POST['password'];
        
        if($email == "email@gmail.com"){
            if($password == "123456"){
                echo "Correctamundo!";
            }else{
                echo "Wrong pass";
            }
        }else{
            echo "Wrong Email";
        }
    }
?>
<!DOCTYPE html>
<html>
    <head>
        <title>Login Form</title>
    </head>
    <body>
        <form method="POST" action="">
            <input type="email" name="email" value="">
            <input type="password" name="password" value="">
            <input type="submit" value="Submit" name="submit">
        </form>
    </body>
</html>

当提交的邮箱为email@gmail.com且密码为123456时，页面会显示**Correctamundo!**提示。

随后我在另一个文件中编写了PHP Curl代码来提交表单，代码如下：

<?php
$data = array(
    "email" => "email@gmail.com",
    "password" => "123456",
    "form" => "submit"
);

$ch = curl_init("http://sitename.com/login.php");
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); // Allow Redirections
curl_setopt($ch, CURLOPT_POST, true); // Making a POST request
curl_setopt($ch, CURLOPT_POSTFIELDS, $data);
curl_setopt($ch, CURLOPT_COOKIEJAR, 'cookie.txt'); // COOKIE-jar: To save data for cookie created for login process
curl_setopt($ch, CURLOPT_COOKIEFILE, 'cookie.txt'); 
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true); // TRUE means Don't just echo output the data instead we can store the Request response in some variable

$result = curl_exec($ch);
curl_close($ch);

echo $result;
?>

我已传入正确的凭据参数，但加载页面时并未得到预期的**Correctamundo!**成功提示，请问问题出在哪里？

你的Curl代码存在一个核心错误：

• 登录页面的PHP逻辑通过isset($_POST['submit'])判断表单是否提交，但你在Curl的$data数组里把触发参数名写成了"form" => "submit"，正确的参数应该对应表单提交按钮的name="submit"和value="Submit"，也就是"submit" => "Submit"。

修正后的$data数组如下：

$data = array(
    "email" => "email@gmail.com",
    "password" => "123456",
    "submit" => "Submit"
);

另外，调试时可以加入Curl错误检查，方便快速定位问题：

$result = curl_exec($ch);
if(curl_errno($ch)){
    echo 'Curl error: ' . curl_error($ch);
}
curl_close($ch);

修改后，Curl提交的参数就能被登录页面的PHP逻辑正确识别，从而返回预期的**Correctamundo!**提示。

内容的提问来源于stack exchange，提问作者Pouya Vaghefi