( string filename )
Returns TRUE if the filename exists and is a symbolic link.
Note: The results of this
function are cached. See clearstatcache() for
Tip: As of PHP 5.0.0 this function
can also be used with some URL wrappers. Refer to
Appendix M for a listing of which wrappers support
stat() family of functionality.
See also is_dir(),
is_file(), and readlink().