imagecreatefromjpeg() php

I'm using imagecreatefromjpeg() function to merge two pictures..

now the problem which I'm facing is that when I use the pictures from my server, it works perfectly and when I use pictures from some other website, it doesn't work.

For example: when I use this PHP file http://coolfbapps.in/test/merger.php with function

 imagecreatefrompng('http://coolfbapps.in/test/1.png');

It works perfectly fine as the image is at my own server

but when I alter this function n put the link of an image which is not on my server,

for example.

  imagecreatefrompng('http://www.businesseconomics/Test.png');

it doesnt work. (the image file is not on my server)

please suggest me an alternative to this function or a solution as I want to use this with Facebook apps..

Functions like file-get-contents are also showing the same error. I hope its not server end problem.. allow_url_fopen is on but allow_url_include is off

Update...Actual code. I'm using this to merger two pictures

 $dest = imagecreatefrompng('http://coolfbapps.in/test/1.png');

 $src = imagejpeg('http://img.allvoices.com/thumbs/image/111/111/75152279-pic.jpg');

 imagealphablending($dest, false);
 imagesavealpha($dest, true);

 imagecopymerge($dest, $src, 10, 9, 0, 0, 181, 180, 100); 

 header('Content-Type: image/png');
 imagepng($dest);

 imagedestroy($dest);
 imagedestroy($src);