PHP

php remove cookie

if (isset($_COOKIE['key'])) {
    unset($_COOKIE['key']);
    setcookie('key', '', time() - 3600, '/'); // empty value and old timestamp
}

remove cookies php

unset($_COOKIE['hello']);

delete all cookies in php

// unset cookies
if (isset($_SERVER['HTTP_COOKIE'])) {
    $cookies = explode(';', $_SERVER['HTTP_COOKIE']);
    foreach($cookies as $cookie) {
        $parts = explode('=', $cookie);
        $name = trim($parts[0]);
        setcookie($name, '', time()-1000);
        setcookie($name, '', time()-1000, '/');
    }
}