Image copy error?

<?php

$top_file = 'image1.jpg';

$bottom_file = 'image2.jpg';

 

$top = imagecreatefromjpeg($top_file);

$bottom = imagecreatefromjpeg($bottom_file);

 

// get current width/height

list($top_width, $top_height) = getimagesize($top_file);

list($bottom_width, $bottom_height) = getimagesize($bottom_file);

 

// compute new width/height

$new_width = ($top_width > $bottom_width) ? $top_width : $bottom_width;

$new_height = $top_height + $bottom_height;

 

// create new image and merge

$new = imagecreate($new_width, $new_height);

imagecopy($new, $top, 0, 0, 0, 0, $top_width, $top_height);

imagecopy($new, $bottom, 0, $top_height+1, 0, 0, $bottom_width, $bottom_height);

 

// save to file

imagejpeg($new, 'uploads/merged_image.jpg');

?>