What is the best practice for checking if a cookie exists and using its data in a PHP session?

To check if a cookie exists and use its data in a PHP session, you can first check if the cookie is set using the isset() function, then retrieve its value using $_COOKIE. If the cookie exists, you can assign its value to a session variable for further use. 

<?php
// Check if the cookie exists
if(isset($_COOKIE['cookie_name'])) {
    // Retrieve the cookie value
    $cookie_value = $_COOKIE['cookie_name'];
    
    // Start or resume the session
    session_start();
    
    // Assign the cookie value to a session variable
    $_SESSION['session_variable'] = $cookie_value;
}
?>

Keywords

cookie session PHP isset $_COOKIE

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