Code for checking if user registration fields have been filled

[JennyKhoo]

I have examined profile.php and found the following line where I think 'homepage' is being entered (it says updated but I assume that includes inserted .. anyway I can check it out):

$userdata->set('homepage', $vbulletin->GPC['homepage']);

My problem is I don't understand how this code works and therefore I don't know how to examine the contents of 'homepage'.

I want to check if 'homepage' has something entered and if it does then exit().

I don't know if I need to write to a temporary variable and check the temporary variable or check something in the code here.

Would you please tell me what code I can use to check to see if 'homepage' is entered when the code in profile.php says:

$userdata->set('homepage', $vbulletin->GPC['homepage']);

The code doesn't have to be brilliant just has to get the job done. If you give me an idea what to write then I can check it you don't have to check it.

Thank you very much for your help.