What are the best practices for handling form validation and data re-population in PHP?

When handling form validation in PHP, it is important to validate user input to ensure data integrity and security. To handle form validation and data re-population, you can use conditional statements to check if the form has been submitted and display error messages if validation fails. To re-populate form fields with user input, you can use the $_POST superglobal array to retrieve the values entered by the user. 

<?php
// Check if form has been submitted
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    // Validate form data
    $name = $_POST["name"];
    if (empty($name)) {
        $nameError = "Name is required";
    }

    // Re-populate form fields with user input
    $nameValue = isset($_POST["name"]) ? $_POST["name"] : '';
}
?>

<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
    <input type="text" name="name" value="<?php echo isset($nameValue) ? $nameValue : ''; ?>">
    <span><?php echo isset($nameError) ? $nameError : ''; ?></span>
    <button type="submit">Submit</button>
</form>

Keywords

form validation data re-population PHP input sanitization error handling

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