Accessibility- text resize button

[marra]

Hi, I'm currently re-developing a charity's website and need to integrate a button to increase or decrease the text size on the page. I have looked at various javascript solutions but would prefer to implement it with php. Does anyone know the best way of doing this? There seems to be several ways documented on the internet but I cannot find a simple effective way. I'm guessing a style sheet switcher would be my best option. Does anyone have any links to code I could use?

Cheers for any help

 

[marra]

The site is currently only using XHTML and CSS and is only an information site so it does not currently have any PHP written or a CMS. Do you have any links to some code I could use? What I want basically is a button for small text, one for medium and another for large. I have designed the site in a way that it expands to accommodate the larger text but just need help in writing the code to actually do it. It works great using the Ctrt +/- in firefox.