For information about the security implications of register_globals, read the security chapter on Using register_globals.

It's preferred to use superglobals, rather than relying upon register_globals being on.

If you are on a shared host with register_globals turned off and need to use some legacy applications, which require this option to be turned on, or you are on some hosting server, where this feature is turned on, but you would like to eliminate security risks, you might need to emulate the opposite setting with PHP. It is always a good idea to first ask if it would be possible to change the option somehow in PHP's configuration, but if it is not possible, then you can use these compatibility snippets.