How to extract segment of video using FFMPEG

Once i had a situation where i had to extract a part (segment) of a video lets say from 3rd second to 8thd second. So after searching through FFMPEG documentation
i came to know how this could be done.
Following code snippet can be used to extract a segment of video.

$inputFile = "melt.mpg";
$outputFile = "melted.flv";
//-ss is the start time in HH:mm:ss
//-t is the end time in HH:mm:ss
system("path-to-ffmpeg/ffmpeg -i $inputFile -ss 00:00:03 -t 00:00:08 $outputFile");

And that's it.

Get total length of Video in PHP

    //Total Length of video can be userful at many cases. Following code sample shows
    // how to get the total length or duration of any video file

    //get the filename of video
    $uploadVideoFile = $_FILE["fleVideo"]["name"];

    //turn on the output buffering
    ob_start();

    //execute the the ffmpef command, where -i is the input
    //the 2>&1 is done to redirect standard error (stderr) to standard output(stdout)
    system("/path/to/ffmpeg -i $uploadVideoFile 2>&1");
    //now get the contents
    $totalDuration = ob_get_contents();

    //clear the output buffer and turn off the output buffering done by ob_start()
    ob_end_clean();

    //perform a regular expression match
    //check for the pattern Duration: ... in $duration and return matches
    preg_match('/Duration: (.*?),/', $duration, $matches);

    //found the matches
    //this is the total length of video
    $totalLength = $matches[1];
    echo "Total Length of the video is:".$totalLength;
?>

PHP Video Conversion & Thumbnail -- FFMPEG

To convert video to flv format add the following code:
$source = "path/somesource.mpg";
$destination = "path/somefilename.flv";
exec("/path/to/ffmpeg -i $source -ab 128 -ar 22050 -b 300000 -r 25 -s 320×240 $destination");

And to generate video first-frame thumbnail, add the following code:
exec("/path/to/ffmpeg -i $source -ss 1.4 -vframes 1 -f image2 $screenshotImg");