Attempts to rename oldname to newname.
Returns TRUE on success or FALSE on failure.
Note: Prior to PHP 4.3.3, rename() could not rename files across partitions on *nix based systems.
Note: As of PHP 5.0.0 rename() can also be used with some URL wrappers. Refer to Appendix M for a listing of which wrappers support rename().
Note: The wrapper used in oldname MUST match the wrapper used in newname.
Note: Context support was added with PHP 5.0.0. For a description of contexts, refer to Reference CLIII, Stream Functions.