How can PHP headers be used to redirect users back to a form page with their previously entered data in case of validation errors?

When a form submission fails validation, we can use PHP headers to redirect users back to the form page with their previously entered data intact. This can be achieved by storing the form data in session variables before redirecting, and then populating the form fields with these session values when the form page is loaded again. 

<?php
session_start();

// Validate form data
if(/* validation fails */) {
    // Store form data in session variables
    $_SESSION['name'] = $_POST['name'];
    $_SESSION['email'] = $_POST['email'];
    
    // Redirect back to form page
    header('Location: form.php');
    exit();
}

// Clear session data after successful form submission
unset($_SESSION['name']);
unset($_SESSION['email']);
?>

Keywords

PHP headers redirect form page validation errors previously entered data

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