String Splitters

A new movie…
Uh, anyway, say I have a string like this:

$num = “Hello 2890. How are you?”;

I want that to be split up so that the number is in a seperate string, as such:

$num_num = “2890”;

Now, I havn’t tried this, but if it’s right, just tell me and I’ll be ashamed for not trying it first; could I do that with a function like this:

$num_num = preg_split("(.?)[0-9]+(.?)", $num);

What confuses me about that is that both the '(.?)*'s would be saved into the string aswell. I think… Anyway, can anyone enlighten me?

edit: or preg_split(".?([0-9])+.?", $num);
That way the '.?*'s wouldn’t be counted as an output thingy… I’ll shut up. I havn’t done this for a while, so I’m a bit rusty…