How to parse and modify the finished PHP/HTML code?

Question

PHP

In general, the question is that I want to put the following process on automatic:
parsing an html page, pre-designed -> adding classes to certain elements -> writing the contents of some tags to the database and then replacing the text in the tags with an array from the database (which would display the same text, but already from the database)
as a result: re-saving all this stuff in a separate php file.

I'm not asking for instructions on how to do this, but rather a hint from those who have already done this or know something.
Is this even possible or should it be done differently? phpQuery will work?