Dealing with dollars (& cents)

I am writing an affiliate program for one of my sites and am having problems figuring out the payments to the affiliates. I am storing all the configurable info in a mysql table. ie....site name, payout........ I am trying to figure out the total payout on the fly for each day. This is the formula that I am using. It is rather simple. $payout[$mcount] = ($stats_result[0] * $result[3]); $mcount is a small counter to count the days while looping. - this works ok. Starts at 1. $stats_result[0] is a count of the total hits for any given day. - this works ok $result[3] is the payout amount. - this works ok. I am using 5.50 for my testing. When I echo each of the above values, they return the correct values. The problem is when I try and do the math. No matter what payout amount I put in the database, it will only return 5. It should return 5.50. Why? Is it the $payout[$mcount] ? Did I explain this good enough? If not let me know and I will try and do better. Thanks CDitty