ffmpeg calculate video duration php function

The following is a php function which uses the software ffmpeg to calculate the time duration of a video :

function calculateDuration($filename){								

		$command = "ffmpeg -i '{$filename}' 2>&1";					

		ob_start();

		passthru($command);

		$content_grabbed = ob_get_contents();

		ob_end_clean();

		$search = '/Duration: (.*?)[.]/';

		$duration = preg_match($search, $content_grabbed, $matches, PREG_OFFSET_CAPTURE);

		$duration = $matches[1][0];

		list($hours, $mins, $secs) = explode(':', $duration);

		if($mins == '' && $secs == ''){			

			return false;

		}

		$hours = intval($hours);

		if ($hours != 0){

			$dur = $hours . ":" . $mins . ":" . $secs;

		}

		else {

			$mins = intval($mins);

			$dur = $mins . ":" . $secs;

		}		

		return $dur;

	}

Use the function as follows :

$filename = 'input.flv';

echo "duration is ".calculateDuration($filename);