Command to back up files on a server?

[Chronicle]

Hi,
What would be the best command to run (Via a cronjob or maybe a php script) to backup all files apart from image files (jpg,jpeg,png,gif) and under 1mb, and zip (or tar.gz) them? I've searched on google but can't come up with anything

thanks

 

[Chronicle]

It is on linux. Do you have any links? I've done some searching on Google but its all either too basic (just taring a whole directory) or far too complicated