How to install and run phpize

I have been meaning to install `ffmpeg` as an extension to my PHP setup. So before I can install it, I need to `phpize` it. I installed `php5-dev` by `sudo apt-get install php5-dev`. But now when I run `phpize` I get the following error : phpize Cannot find config.m4. Make sure that you run '/usr/bin/phpize' in the top level source directory of the module The location of my php.ini is `/usr/local/zend/etc/php.ini` From another online resource I tried this sudo apt-get install autoconf automake libtool m4 But all of them are already installed. Locate config.m4 didn't return anything. Any pointers here how I can get `phpize` and thus, `ffmpeg` up and running?