Checking what PHP version I'm running on Linux?

Try running the following at the command line.

To just get the version information:

php -v

Or to get a lot of info:

php -i

It should give you all information you need about the php install.

You can make an index.php file with

<?php phpinfo() ?>

An answer was accepted, but another option on RPM systems (RHEL, Centos, Fedora, etc.) is to use the following:

rpm -q php

And while I'm at it, the general method for using RPM to find info on a package for any rpm-installed program or file is similar to this (for awk):

1. Find the full path to the file if not known, such as for an executable in $PATH:

   type -path awk

2. Find the name, including version, of the package containing the file:

   rpm -qf /usr/bin/awk

3. If desired, query for info from that package:

   rpm -qi gawk

It's a bit trickier for packages installed and used by Apache since they may not be on $PATH, but you can start with something like:

rpm -qa | egrep -i 'php|awk'