sort multidim array

I've been banging my head against the wall on this one. Probably trivial to the knowledgeable, but I'm stumped despite trying the various sort functions as advertised on php.net. I've got the following fields: retailer city state telephone distance Sample data looks like: BLIND BROOK CLUB PURCHASE, NY (914) 939-1450 4.6 BURNING TREE CC GREENWICH, CT (203) 869-9010 0 CENTURY COUNTRY CLUB PURCHASE, NY (914) 761-0400 4.6 FAIRVIEW CC GREENWICH, CT (203) 531-4283 2.2 ...... All of this is in an array I'll call $zipArray. When I get the data from mysql, it doesn't contain the 'distance' info. The distance field is calculated and tacked onto each row by having everything go through a foreach loop. So I start with an array that has 4 data columns (retailer, city, state and telephone) and I end up with an array that has 5 data columns (retailer, city, state, telephone, and distance). If I apply asort($zipArray) it sorts nicely on the first data column - retailer. But I need it to sort on the last data column - distance. I think I've been staring at this too long. Would appreciate any guidance. Thanks Kevin --