Is lima-city a hosting service? if so, where and how did you load php? And if you have control over php, and you installed a new version of php, then you have to restart the web server after upgrading to a new version.
This function has been available since version 4 of php. So it's unlikely that it is not included in the php distribution being used on the server.
If lima-city is a web hosting service, it is possible that for some reason this service has disabled this function. See:
http://ca2.php.net/manual/en/ini.core.php#ini.disable-functions
And contact the hosting service.