portmidi is a portable real-time MIDI library. portmidi-php is a wrapper extension that provides portmidi functionality in PHP land.
To install:
$ sudo apt-get install libportmidi-dev # or equivalent
$
$ # Clone repo
$ git clone https://github.com/adsr/portmidi-php.git
$ cd portmidi-php
$
$ # Build extension
$ phpize && ./configure && make
$
$ # Run demo
$ php -denable_dl=on -dextension=`pwd`/modules/portmidi.so examples/portmidi.php
$
$ # Optionally install
$ sudo make install