[TYPO3-english] How to debug while creating extensions

[Jeppe Donslund]

Hi.

I get this error while creating an extension:

Warning: array_merge() [function.array-merge]: Argument #2 is not an 
array in 
/var/www/www.mydomain.dk/www/typo3/sysext/cms/tslib/class.tslib_pibase.php 
on line 507

Are the any tools or extensions I can use to debug my extension to find 
out why this error occurs?

Best regards
Jeppe Donslund