Joomla - editing default flow of submitting adverts.

[daydreamer]

Hi,

 

I need to change the default flow of a form in Joomla. (it is a marketplace component, which allows users to create adverts).

 

Currently it just posts the adverts.

 

I want to put my own PHP in that checks if a user has paid a fee, if they have post their ad, if not redirect them to a Paypal payment page.

 

The page is

index.php?option=com_marketplace&page=write_ad&Itemid=10

 

Where is the PHP code that processes this form located? Can I just put my own PHP in?

 

I have checked index.php, but the Joomla framework of PHP files is complicated, with hundreds of includes.

 

Thanks.