I would like to merge several videos using ffmpeg and php. I want to retrieve the names of the videos dynamically but I can't merge all the videos together I only get i-1 merged videos This is the code I use:

<?php
$checkBox = $_POST['language'];
$output=rand();

function conv($checkBox){
$tab=array();
    for($i=0; $i<sizeof($checkBox); $i++)
    {

        $intermediate=rand();

        $tab[$i]=$intermediate;
        exec("C:\\ffmpeg\\bin\\ffmpeg -i C:\\wamp\\www\\video_qnb\\model\\input\\$checkBox[$i].mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts C:\\wamp\\www\\video_qnb\\model\\output\\$intermediate.ts");

    }
    return $tab;
}

$t=conv($checkBox);

for($i=0;$i<sizeof($t); $i++)
{
if($i!=0)
{

    if(sizeof($t)<=2)
    {
        exec('C:\\ffmpeg\\bin\\ffmpeg -i "concat:C:\\wamp\\www\\video_qnb\\model\\output\\'.$t[$i-1].'.ts|C:\\wamp\\www\\video_qnb\\model\\output\\'.$t[$i].'.ts" -c copy -bsf:a aac_adtstoasc C:\\wamp\\www\\video_qnb\\model\\output\\'.$output.'.mp4');
    }
    else
    {
         exec('C:\\ffmpeg\\bin\\ffmpeg -i "concat:C:\\wamp\\www\\video_qnb\\model\\output\\'.$t[$i-1].'.ts|C:\\wamp\\www\\video_qnb\\model\\output\\'.$t[$i].'.ts" -c copy -bsf:a aac_adtstoasc C:\\wamp\\www\\video_qnb\\model\\output\\'.$output.'.mp4');
        exec("C:\\ffmpeg\\bin\\ffmpeg -i C:\\wamp\\www\\video_qnb\\model\\output\\".$output.".mp4 -c copy -bsf:v h264_mp4toannexb -f mpegts C:\\wamp\\www\\video_qnb\\model\\output\\i.ts");
         exec('C:\\ffmpeg\\bin\\ffmpeg -i "concat:C:\\wamp\\www\\video_qnb\\model\\output\\i.ts|C:\\wamp\\www\\video_qnb\\model\\output\\'.$t[$i+1].'.ts" -c copy -bsf:a aac_adtstoasc C:\\wamp\\www\\video_qnb\\model\\output\\final.mp4');
        $i++;
    }
}
}
?>

Can anyone help me??