function _x() not working within custom functions

[froot]

I'm used to use _x('string', 'category') to fill all my language dependent needs with strings in templates.

Now that I use a custom written php function that is included, this _x() function doesn't work anymore. 

#0 SITE/TEMPLATES/REFERENT.PHP
(57): INCLUDE()
#1 WIRE/CORE/TEMPLATEFILE.PHP (318): REQUIRE('/APPLICATIONS/M...')
#2 WIRE/CORE/WIRE.PHP (394): TEMPLATEFILE->___RENDER()
#3 WIRE/CORE/WIREHOOKS.PHP (823): WIRE->_CALLMETHOD('___RENDER', ARRAY)
#4 WIRE/CORE/WIRE.PHP (465): WIREHOOKS->RUNHOOKS(OBJECT(TEMPLATEFILE), 'RENDER', ARRAY)
#5 WIRE/MODULES/PAGERENDER.MODULE (536): WIRE->__CALL('RENDER', ARRAY)
#6 WIRE/CORE/WIRE.PHP (397): PAGERENDER->___RENDERPAGE(OBJECT(HOOKEVENT))
#7 WIRE/CORE/WIREHOOKS.PHP (823): WIRE->_CAL (LINE 29 OF SITE/TEMPLATES/_FOOT.PHP)
THIS ERROR MESSAGE WAS SHOWN BECAUSE: SITE IS IN DEBUG MODE. ($CONFIG->DEBUG = TRUE; => SITE/CONFIG.PHP). ERROR HAS BEEN LOGGED.

any ideas?

[Ivan Gretsky]

How are you including this function? Is it in ProcessWire namespace?