Before installing FFmpeg-PHP, you need to install FFmpeg, MPlayer and MEncoder for video processing.
I posted an installation guide for them. You can reach it from this post:

Because I have CPanel on my CentOS, I won’t install Apache, MySQL or PHP. I’m just going with FFmpeg-PHP installation.
If you need Ruby on Rails, you can also install it via CPanel scripts.

So I assume you did previous installations. Now let’s go with FFmpeg-PHP installation.

1. Download ffmpeg-php in to /usr/src directory.

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cd /usr/src
wget http://downloads.sourceforge.net/project/ffmpeg-php/ffmpeg-php/0.6.0/ffmpeg-php-0.6.0.tbz2?r=&ts=1365651935&use_mirror=garr