Generating a random url

i have a app which print a name in photo and generates a random image problem is I can not implement the share button every time is the same link and the image is frist image indexed not change on evry refresh because the link is same for example http://ift.tt/YJQuEs how to generate a random link ex http://ift.tt/1Qpm55b or /12354.php evry time when page is loading to generate a random link .sorry my bad english