<?php
    $host = 'localhost';
    $db   = 'hftest';
    $user = 'hftestzone';
    $pass = 'NLXSAii5N9Ukaujk';
    $charset = 'utf8mb4';

    $dsn = "mysql:host=$host;dbname=$db;charset=$charset";
    $opt = [
        PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
        PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
        PDO::ATTR_EMULATE_PREPARES   => false,
    ];
    $pdo = new PDO($dsn, $user, $pass, $opt);

    $message = "Hello";
    $stmt = $pdo->prepare('SELECT * FROM tkeys WHERE tkey = :tkey');
    $stmt->execute(['tkey' => $tkey]);
    $user = $stmt->fetch();

    if($user){
        $sql = "UPDATE tkeys SET tkey = NULL WHERE tkey = ?";
        $pdo->prepare($sql)->execute([$user["message"]]);
        echo "Complete.";
    }else{
        echo "No message.";
    }
?>