public function getTrackNumber()
    {
        if ($this->trackNumber === null) {
            $match = [];
            preg_match(self::$REGEX_TRACK_NUMBER, $this->output, $match);
            $this->trackNumber = (int)(array_key_exists(2, $match) ? $match[2] : 0);
        }

        return $this->trackNumber;
    }
public function getTrackNumber()
    {
        if ($this->trackNumber === null) {
            $match = [];
            preg_match(self::$REGEX_TRACK_NUMBER, $this->output, $match);
            $this->trackNumber = (int)(array_key_exists(2, $match) ? $match[2] : 0);
        }

        return $this->trackNumber;
    }
public function getTrackNumber ( ) { if ( $ this -> trackNumber === null ) { $ match = [ ] ; preg_match ( self :: $ REGEX_TRACK_NUMBER , $ this -> output , $ match ) ; $ this -> trackNumber = ( int ) ( array_key_exists ( 2 , $ match ) ? $ match [ 2 ] : 0 ) ; } return $ this -> trackNumber ; }
Return the track ID3 field from an mp3 file.

@return int
Return the track ID3 field from an mp3 file .