need to know how do u get the image source from the image url for 3rd party videos

I am new to drupal and php.
I am working on a block module in which I only have the image url and I do want to get the image source so that I can connect to the image on the third party images and show it in the block.

I really do not know how do u convert image url to get the image source.
I have gone through ur module but I have not been able to figure it out.

I would really appreciate if u could take some precious time to help.
Thanks.

Regards
JUNED KAZI