Check array for partial match (PHP)

Check array for partial match (PHP)

I have an array of filenames which I need to check against a code, for
example
array("120_120_435645.jpg","150_150_312312.jpg","250_250_1232327.jpg");
the string is "312312" so it would match "150_150_312312.jpg" as it
contains that string.
I tried in_array but this seems to any return true if it is an exact match.
Thanks for any advice...perhaps I have been staring at it too long and a
coffee may help :)