php alert

// This is in the PHP file and sends a Javascript alert to the client
$message = "Something";
echo "<script type='text/javascript'>alert('$message');</script>";

// This is in the PHP file and sends a Javascript alert to the client
$message = "wrong answer";
echo "<script type='text/javascript'>alert('$message');</script>";

echo '<script type="text/javascript">alert("'.$error.'");</script>';