private function _checkProhibitedFunctions($functionName) {
		if ($this->_isActive('checkProhibitedFunctions')) {
			if (in_array($functionName, $this->_prohibitedFunctions)) {
				$msg = $this->_getMessage('PROHIBITED_FUNCTION', $functionName);
				$this->_writeError('checkProhibitedFunctions', $msg);
			}
		}
	}