ffmpeg create video thumbnail php function

The following code is a php function which creates a thumbnail of a video using ffmpeg

function  createVideoThumbnail($video_filename,$size,$output_name){	

		$command = "ffmpeg -i '{$video_filename}' -r 1 -ss 00:00:05 {$size} -f image2 '{$output_name}'";					

		ob_start();

		passthru($command);

		$content_grabbed = ob_get_contents();

		ob_end_clean();

		if(!file_exists($output_name)){			

			return false;

		}		

		return true;		

	}  		

Use the function as follows :

	$video_filename = 'input.mp4';

	$size = '120x72';

	$output_name = 'output.jpg';

	createVideoThumbnail($video_filename,$size,$output_name);