Add html attributes to a tag via PHP

I was wondering if there was a way to do this rather than make my own function, I have a tag like

 
<img src="image.jpg">

and I need to add attributes to it, sometimes more than one, like height=x and width=x sometimes, but not others.

So a tag in that format is stored in my database column, and I need to modify them on the fly, any ideas?

Does this work for you?
http://www.php.net/manual/en/domdocument.createattribute.php

See domdocument library and its examples in user notes.

Is that much necessary? I’m not looking to create a new document or anything, simply take an image tag and add a few attributes, thought it seemed more like string manipulation.

On second thought, I just decided to delete all records and change up how I store the image url, storing it as a plain url so I can later format it however I want it.