Difference between session_register and $_SESSION[]

Question

What is the difference between session_register() and $_SESSION array ?

Answer 1

From the manual page for session_register:

This function has been DEPRECATED as of PHP 5.3.0. Relying on this feature is highly discouraged.

There are differences (e.g., session_register accepts names of global variables, automatically starts the session, etc), but I think a sufficient answer is "don't use session_register" unless you really want to know the list of caveats for educational purposes.

Just to elaborate on one point that makes session_register bad: it relies on global variables (and register_globals).