private function checkIdField() {
	if(is_null($this->headers)) {
		return;
	}
	if(in_array($this->idField, $this->headers)) {
		return;
	}

	foreach($this->headers as $header) {
		if(strtolower($this->idField) == strtolower($header)) {
			$this->setIdField($header);
		}
	}
}