Getting black screen after merging my images in PHP

image 1 image 2

When I am merging the images I am getting the image like this:merged image

Here is my code:

$topFile = imagecreatefromjpeg($strTopFilePath);
$bottomFile = imagecreatefromjpeg($strBottomFilePath);

list($intTopFileWidth, $intTopFileHeight) = getimagesize($strTopFilePath);
list($intBottomFileWidth, $intBottonFileHeight) = getimagesize($strBottomFilePath);

// compute new width/height
$intNewFileWidth = ($intTopFileWidth > $intBottomFileWidth) ? $intTopFileWidth : $intBottomFileWidth;     
$intNewFileHeight = $intTopFileHeight + $intBottonFileHeight;
// create new image and merge

$new = imagecreatetruecolor($intNewFileWidth, $intNewFileHeight);
imagecopy($new, $topFile, 0, 0, 0, 0, $intTopFileWidth, $intTopFileHeight);
imagecopy($new, $bottomFile, 0, $intTopFileHeight+1, 0, 0, $intBottomFileWidth, $intBottonFileHeight);
imagejpeg($new, $strMergedPath);

Please help. Thanks in Advance.