注意：未定义索引 $_POST 方法

问：

我有一个php简单的项目。 该项目是创建一个电子邮件提交页面。 我使用phpstorm软件。

        <?php
        //get user input
        $name = $_POST["name"];
        $email = $_POST["email"];
        $message = $_POST["message"];
        //error message
        $missingName = '<p><strong>Please enter your name</strong></p>';
        $missingEmail = '<p><strong>Please enter your email address</strong></p>';
        $invalidEmail = '<p><strong>Please enter a valid email address</strong></p>';
        $missingMessage = '<p><strong>Please enter a message</strong></p>';
        //if the user has submitted the form
        if ($_POST["submit"]){
            //check for errors
            if (!$name){
                $errors .= $missingName;
            }else{
                filter_var($name, FILTER_SANITIZE_STRING);
            }
            if (!$email){
                $errors .= $missingEmail;
            }else{
                filter_var($email, FILTER_SANITIZE_EMAIL);
                if (!filter_var($invalidEmail, FILTER_VALIDATE_EMAIL)){
                    $errors .= $invalidEmail;
                }
            }
            if (!$message){
                $errors .= $missingMessage;
            }else{
                $message = filter_var($message, FILTER_SANITIZE_STRING);
            }
            //if there are any errors
            if ($errors){
                $resultMessage = '<div class="alert alert-danger">' . $errors . '</div>';
            }

        }
        ?>
        <form action="index.php" method="post">
            <div class="form-group">
                <label for="name">Name:</label>
                <input type="text" name="name" placeholder="Name" id="name" class="form-control">
            </div>
            <div class="form-group">
                <label for="email">Email:</label>
                <input type="text" name="email" placeholder="Email" id="email" class="form-control">
            </div>
            <div class="form-group">
                <label for="message">Message:</label>
                <textarea name="message" id="message" class="form-control" rows="5"></textarea>
            </div>
            <input type="submit" name="submit" id="submit" class="btn btn-success btn-lg" value="Send Message">
        </form>

当我运行项目时，我遇到了您在图像中看到的错误

错误消息

错误来自以下行

$name = $_POST["name"];
$email = $_POST["email"];
$message = $_POST["message"];

而这条线

if ($_POST["submit"])

请帮忙！