Please, please, please, use phpversion to ensure that php is not version 4.x before mapping/geocodding can be enabled.
Otherwise your client will decide to check out this fancy feature on the production server and not tell you. They'll then complain that they can't save changes to contact records, they just get a blank screen. You'll then go about comparing the code differences between the production and staging servers, SVN diffs, comparing memory usage. Oh the humanity. Of course you tried to enable error logging to screen, but it was overridden further up the stack. You and two other developers will eventually get it figured out, in a few hours. But this all could have been avoided with a simple check to phpversion.