How can sessions or hidden fields be utilized in PHP to retain values across form submissions?

To retain values across form submissions in PHP, sessions or hidden fields can be utilized. Sessions store data on the server side, allowing information to persist across different pages or form submissions. Hidden fields, on the other hand, store data within the form itself, allowing values to be passed along with the form submission. 

// Using sessions to retain values across form submissions
session_start();

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $_SESSION['username'] = $_POST['username'];
}

// Using hidden fields to retain values across form submissions
<form method="post" action="">
    <input type="hidden" name="username" value="<?php echo isset($_POST['username']) ? $_POST['username'] : ''; ?>">
</form>

Keywords

sessions hidden fields PHP form submissions retain values

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