question regarding content search in array with PHP

Hello list,

I have an array that for the example will look as follows:

linux, windows, mac os, beos, os/2, freebsd, netbsd, irix ....

And a string:

"linux kernel 2.6.24"

Now I wish to find the closest value of the string in the array -> "linux".
But the problem as you can see, is that the string contain more
content then the array value.
I can think on many unefficient ways to find the part of string as an
array value, but I'm looking for an efficient way to do it. specially
if I need to serve a lot of strings on after the other...
The problem is, that I must use PHP (because I can think on an answer
using Perl, that I haven't tested).

Any ideas how I can do it in an efficient way ?

Thanks,
Ido
-- 
http://ik.homelinux.org/