php中的imagecreatefromjpeg（）函数

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 and put the link of an image which is not on my server,

for example:

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

it doesn't 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..

You can use the PHP Function copy() to save the image on your Server.