Image Resize and save by using GD function and Percentage based

<?php
$filename = 'test.jpg';
$percent = .5;
list($width, $height) = getimagesize($filename);
$newwidth = $width * $percent;
$newheight = $height * $percent;
$thumb = imagecreatetruecolor($newwidth, $newheight);
$source = imagecreatefromjpeg($filename);
imagecopyresized($thumb, $source, 0, 0, 0, 0, $newwidth, $newheight, $width, $height);
$ourFileName = "newtest.jpg";
imagejpeg($thumb, $ourFileName);
imagedestroy($thumb);
?>