Like keeping current with WordPress, your themes and plugins its also important to keep current with your version of PHP. When PHP is updated its very likely that things will work if you are using a previous version but you won’t get all of the functionality of the new version and the old one might have some bugs or problems that are corrected in the new version.
To see what version of PHP you have you will need to look at your hosting server. When you log into your cpanel you should be able to see what php version you are using, the most current stable version right now is 5.6.11.
Your homework now is to go and see what version of php you have. If you see that you need an update, talk with your web person or your hosting company.