What are some common methods to retain form data in PHP after submitting and displaying error messages?

When submitting a form in PHP and displaying error messages, it is important to retain the form data that the user entered so they do not have to re-enter everything. One common method to achieve this is by using the $_POST superglobal array to populate the form fields with the previously submitted data. 

<?php
// Initialize variables to store form data
$name = '';
$email = '';

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Retrieve form data
    $name = $_POST['name'];
    $email = $_POST['email'];
    
    // Validate form data
    if (empty($name)) {
        $error = "Name is required";
    }

    if (empty($email)) {
        $error = "Email is required";
    }
}
?>

<form method="post">
    <input type="text" name="name" value="<?php echo $name; ?>" placeholder="Name">
    <input type="email" name="email" value="<?php echo $email; ?>" placeholder="Email">
    <button type="submit">Submit</button>
</form>

<?php
// Display error messages
if (isset($error)) {
    echo $error;
}
?>

Keywords

session variables form validation error handling POST method input sanitization

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