How to hide file path using PHP

[said_fox]

Hi,
I would like to ask about how to, randomly, hide a file path using PHP and what is the technical name of such process.

For example:
mywebsite.com/imgs/someuser/img.jpg
to
mywebsite.com/imgs/nddsfdsfgdfuu4923fdj3er982/img.jpg
while the value nddsfdsfgdfuu4923fdj3er982 should be randomly changed every time the img.jpg is requested.

[ssystems]

Create a random salt and store it somewhere, db perhaps, then encode the parameter with the salt. Then use mod_rewrite to rewrite it in a form like mywebsite.com/imagehandler?f=img.jpg&e=<encoded parameter>Have imagehandler compare the parameter to your salt then spit out the object