Well i got some weird problem here .
We have a web team and we disributed our work equally , where i mainly created the web application in php and i am glad its working file . But for simplicity purpose i used basic html tags and created the web app .

Now the designers have completed the front end with CSS and HTML .
Now , i dont have the slightest idea on how to go about using the front end my designers have made. i would be glad if u could provide some valuable suggestions .

It depends on the relationship between the two. If the front-end (for example) has forms that call processing modules, then one or more of your PHP programs will become the "action" on the form statement(s) in the front end. There probably has to be some action by the user in the front end that will trigger your programs. That is probably going to be a form or a link in a menu. If it is more complicated than that, then you might be into wrapping their html & css in some php so you can "include" some of your modules.

its more complicated than that . its not just forms .
i thought i could integrate it , but my php app became a bit compicated .
there is a different headers and one of them i have mainly dedicated to all the functions , which i call using incclude_once.

The problem is in the functions itself , for simplicity i displayed the dats extracted from DB and using basic html tags in echo function.

Later the design was initiated and now , i dont know how to intergrate my php code with the existing page designed .

Will I have to re write my COde again . ?