This can be found in your cpanel on the left column near where the server status link is. You can also create a file that will tell you exactly what you are running.
1.) Login to Cpanel
2.) Select File Manager
3.) Select your Public_HTML folder
4.) Select "create new file"
5.) Name your new file phpinfo.php.
6.) Edit the file. (this will be in a new window)
7.) Type the following in and hit "save" at the bottom.
// Show all information, defaults to INFO_ALL
8.) Now, in a new browser type in www.yoursite.com/phpinfo.php
9.) It should then tell you all about what version of PHP you are running.
10.) When you're done, be sure to remove the file, as it can provide helpful information to hackers about your site.