How can PHP be used to handle client-side input validation in a form submission process?

Client-side input validation can be handled using PHP by writing validation logic in the server-side script that processes the form submission. This way, even if a user bypasses client-side validation or submits the form without JavaScript enabled, the server-side validation will ensure that only valid data is accepted. 

// Server-side validation example
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    $email = $_POST["email"];
    
    // Validate name
    if (empty($name)) {
        $errors[] = "Name is required";
    }
    
    // Validate email
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        $errors[] = "Invalid email format";
    }
    
    // If there are errors, display them
    if (!empty($errors)) {
        foreach ($errors as $error) {
            echo $error . "<br>";
        }
    } else {
        // Process form submission
        // Insert data into database, send email, etc.
    }
}

Keywords

PHP client-side input validation form submission error handling

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