You can run PHP on many different operating systems. All discussion here will deal with Linux. Although most of the concepts discussed are applicable to other OSes, the scripts presented here have only been tested on Linux.
To ensure that PHP has been installed on your machine, type the following:
which php
You should receive a response identical (or similar) to
/usr/bin/php
which shows the path to the executable program.
You can also use
locate php
to find all files accessible to you on your system which contain "php" in their names.