Concatenate videos with fmmpeg in php

I'm making a web site where the users record some videos in a session (4 or 5) with their webcam. The videos are hosted on the site in flv format then uploaded to youtube by an internal process. Now, things have changed so, users still upload videos but once they have uploaded the videos, instead of uploading 3 or 4 or 5 videos separately to youtube i need to concatenate them and then send only one to youtube. I have installed ffmpeg on the website but although I have tried, i couldnt concatenate them in one. I used ffmpeg -i concat:[login to view URL]|[login to view URL] -c copy [login to view URL] but ffmpeg says that "concat:[login to view URL]|[login to view URL]" no such file or directoy. FFmpeg "thinks" that all the string is the file. Perhaps i dont know how to use this command but im tired of trying so if a person can help me. To summarize, you will only have to concatenate the flv videos, you WON'T have to send them to youtube. If ffmpeg doesnt support concatenating flv, you can turn them into mpg and then concatenate them into a mpg. - I will give you access to the ftp. - You will have my php page where i tried the script. - You will have some videos to try. $output = exec("/usr/local/bin/ffmpeg -i 'concat:[login to view URL]|[login to view URL]' -c copy [login to view URL] 2>&1"); concat:[login to view URL]|[login to view URL]: no such file or directory <-- why concat doesnt work??