I've noticed that there are many functions lately on php.net that when I try to use them locally I get

Fatal error: Call to undefined function: function_name() in d:\web\apache\htdocs\test\test.php on line 3

Why is it doing this? I'm using version 4.3.2
I've had this happen with:

stream_socket_server()
socket_get_status()

And so on. Anyone know why? Some say they are experimental but not all.