[TYPO3] How to access a specific plugin function?

[Matthew Manderson]

Hello Peter,

> Did you include the file/class?
Should I need to? given it is in an extension. The main class is outputting
no problem. But I need to call a specific function in it.

Anyway I so tried including the file using:

#include the php script
includeLibs.orderForm = EXT:orderFormMM/pi1/class.tx_orderFormMM_pi1.php

and then 

#include the php script
includeLibs.orderForm =
typo3conf/ext/orderFormMM/pi1/class.tx_orderFormMM_pi1.php

Cleared caches etc but still no $content showing in the front end;
:-(