[TYPO3-UG Cambodia] How to call a function in other class which return the form?

[Chanratha LY]

Dear Typo3Cambodia Members,

I have met one problem and would like to ask all of you.

I have two classes, A & B.
Class A has a function "user_registration" which returns the registration
form.

In B, I would like to call function "user_registration" from class A. It
work well if function "user_registration" returns value.
*Problem:*
It does not work for if function "user_registration" return the form. The
message is: *Fatal error**: Call to a member function typoLink() on a
non-object in **
/home/public_html/first_test/typo3/sysext/cms/tslib/class.tslib_pibase.php**on
line
**309.*

Thanks,
Chanratha