How can PHP and MySQL be used together to retain user selections in option fields after a form submission error or validation failure?

When a form submission error or validation failure occurs, the user's selections in option fields can be retained by using PHP to store the submitted values in session variables and then pre-populating the form fields with these values. This ensures that the user does not have to re-enter all the information after an error. 

<?php
session_start();

// Check if form is submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Store form values in session variables
    $_SESSION['selected_option'] = $_POST['option_field'];
    // Add validation logic here
    // If validation fails, redirect back to the form page
    // Use the stored session values to pre-populate the form fields
}

// Display form with option field
?>
<form method="post" action="">
    <select name="option_field">
        <option value="option1" <?php if(isset($_SESSION['selected_option']) && $_SESSION['selected_option'] == 'option1') { echo 'selected'; } ?>>Option 1</option>
        <option value="option2" <?php if(isset($_SESSION['selected_option']) && $_SESSION['selected_option'] == 'option2') { echo 'selected'; } ?>>Option 2</option>
        <option value="option3" <?php if(isset($_SESSION['selected_option']) && $_SESSION['selected_option'] == 'option3') { echo 'selected'; } ?>>Option 3</option>
    </select>
    <input type="submit" value="Submit">
</form>

Keywords

PHP MySQL form submission validation failure user selections

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