public function getAttributeKeys($class = null) {
		foreach($this as $key => $data) {
			if($class) {
				if($data instanceof $class)
					$ret[] = $key;
			} else {
				$ret[] = $key;
			}
		}
		return $ret;
	}
public function getAttributeKeys($class = null) {
		foreach($this as $key => $data) {
			if($class) {
				if($data instanceof $class)
					$ret[] = $key;
			} else {
				$ret[] = $key;
			}
		}
		return $ret;
	}
public function getAttributeKeys ( $ class = null ) { foreach ( $ this as $ key => $ data ) { if ( $ class ) { if ( $ data instanceof $ class ) $ ret [ ] = $ key ; } else { $ ret [ ] = $ key ; } } return $ ret ; }
Returns the Keys of the Object attributes.

@param string $class Filter only attributes instance of $class.

@return array(int => string)
Returns the Keys of the Object attributes .