You won't run into problems like that, if I'm understanding you correctly. The data can't be 'hidden' or 'private' like it can in other languages, but you shouldn't run into any naming conflicts.
If you have a class called 'User' and some variables inside called:
$userID
$userName
$userEmail
You won't call them in your main app by $userID, etc. - you will call them with the name of the instantiated object like:
$myUser->userID
And really, it's convention not to access the variables directly, but rather use set and get methods which can perform error checking and whatnot on the data you're trying to insert.