Offseting Binary File Data with php

I need to figure out a way to iterate through a binary file and offset values between two address by a fixed number //------- Why ? I am attempting to add file data to a pre-existing Quicktime file.... In the Quicktime file format, the 'stco' atom stores the location of all the track data in the Quicktime file If I add new data, all the 'stco' locations will be incorrect So, basically, I need to change all the offsets here is a picture of the stco data that needs to be offset http://www.siren.cc/code/stcoTable.gif here is the HEX data representation of the stco atom in a hex editor: http://www.siren.cc/code/stco_data.gif //------ Are there any good php tutorials out there that deal with binary/hex operations of this sort ? Thus far, I have not seen many tutorials featuring functions like bin2hex(), pack, and unpack I am a bit new to binary so any help is appreciated :) g