Greyhound is written in CLI PHP. It uses some PHP features that aren't standard in some distributions; however we've found that the majority of large Linux distributions - specifically, Ubuntu and Fedora - have support for these PHP functions either in their respective repositories or out of the box.
Before you can run Greyhound, you'll need to install the CLI version of the PHP interpreter. To do this, open a terminal window and type:
sudo apt-get install php5-cli
Or you can click here to attempt to install the CLI interpreter automatically.
PHP's built-in socket functions don't provide the functionality Greyhound needs to bind to ports and perform other server-related tasks, so it uses PHP's advanced socket functions for this. This library is supported by default in both Ubuntu 8.04 and Fedora 9.
UNIX process control
Greyhound's webserver is multi-threaded, so it needs to be able to call fork() when a new request comes in. This function is provided by the process control library. This is provided automatically by Fedora, while it is installed as a part of php5-cli in Ubuntu.