There's no built-in functions exactly for what you want to do so what you need to do is build some code of your own.
First take a look at the date/time functions of PHP . If I'm going to check the month against a textual month I would use something like this
$st = time(); // gets the current time in unix timestamp
$current_month_full = date("F"); // gets full length month like January, December
$current_month_short = date("M"); // gets abbreviated month like Jan, Dec
$current_month_num_zero = date("m"); // gets current month number with leading 0 like 01, 02
$current_month_num = date("n"); // gets the current month number without leading 0 like 1, 2, 3
// now you need to check against some entered month for example
if($_GET['monthdata'] == $current_month_full){
echo "The month matches the current month!";
}else{
echo "The month does not match the current month!";
}
I hope that gives you some direction.