Checking if image is same image

imageFilter.php

<?php
function getImageHash($filename){
	$content=file_get_contents($filename);
	if($content){
		list($width,$height,$type,$attr)=getimagesize($filename);
		$im=imagecreatefromstring($content);
		$new=imagecreatetruecolor($width,$height);
		imagecopy($new,$im,0,0,0,0,$width,$height,$width,$height);
		imagedestroy($im);
		ob_start();
		imagegif($new);
		$data=ob_get_contents();
		ob_end_clean();
		imagedestroy($new);
		return md5($data);
	}
	return "";
}
$hash=getImageHash("test.jpg");
$hash2=getImageHash("test.png");
if($hash==$hash2){
	echo "Same Image";
}else{
	echo "Different Image";
}
?>