public function getPropertiesNames() {
		$propertiesList = [];
		
		foreach($this->_data as $item) {
			$propertiesList += array_keys($item);
		}
		
		return $propertiesList;
	}
public function getPropertiesNames() {
		$propertiesList = [];
		
		foreach($this->_data as $item) {
			$propertiesList += array_keys($item);
		}
		
		return $propertiesList;
	}
public function getPropertiesNames ( ) { $ propertiesList = [ ] ; foreach ( $ this -> _data as $ item ) { $ propertiesList += array_keys ( $ item ) ; } return $ propertiesList ; }
Get a list of objects' properties

@return array
Get a list of objects properties