function next_dependency(){
		foreach( $this->dependencies as $path => $done ){
			if( ! $done ){
				$this->dependencies[$path] = 1;
				return $path;
			}
		}
		// none
		return null;
	}
function next_dependency(){
		foreach( $this->dependencies as $path => $done ){
			if( ! $done ){
				$this->dependencies[$path] = 1;
				return $path;
			}
		}
		// none
		return null;
	}
function next_dependency ( ) { foreach ( $ this -> dependencies as $ path => $ done ) { if ( ! $ done ) { $ this -> dependencies [ $ path ] = 1 ; return $ path ; } } // none return null ; }
get next dependant file and flag as done
@return string
get next dependant file and flag as done