[Hampshire] [OT] Can anyone help me with some PHP?

Hi All.

Sorry for the OT post - but seeing as it's so busy on here anyway ... :-)

I'm trying to put a PHP app on a server, and it's barfing. The line in
question is :-

$employees[0] = _('None');

The underscore is being seen as an undefined function.

Knowing nothing about PHP, this has defeated me - is this a builtin?
Should it be defined somewhere? Google doesn't say much of any use when
you try searching for punctuation...

Thanks in advance...

Vic.