Most Unix (and Linux) operating systems and distributions have a packaged version of PHP and extensions available through their packaging system. There are sections with basic information on installing PHP using those systems.
For some distributions, there are also third-party repositories of packages that generally include a wider variety of available versions and extensions.
PHP can also be installed as a component of some third-party application servers .
Finally, PHP can always be installed from the source distributions, which allows the greatest flexibility in choosing what features, extensions, and server APIs to enable. There are sections with information about compiling and configuring PHP to use with different server APIs in particular.