php preg_match between bracket

i want to use preg_match to find text between bracket for example: $varx = "(xx)";

final output will be $match = 'xx';

another example $varx = "bla bla (yy) bla bla";

final output will be something like this $match = 'yy';

in other words it strips out bracket. i'm still confusing with regular expression but found that sometimes preg match is more simple solution. searching other example but not meet my need.