I finally had to do it – Optimize lat/long searches.

The method I used is not original, but I did survey MANY suggestions, including mysql spatial data types.

end result:

function getBoundingBox($lat_degrees,$lon_degrees,$distance_in_miles) {
$radius = 3963.1; // of earth in miles
// bearings – FIX
$due_north = deg2rad(0);
$due_south = deg2rad(180);
$due_east = deg2rad(90);
$due_west = deg2rad(270);
// convert latitude and longitude into radians
$lat_r = deg2rad($lat_degrees);
$lon_r = deg2rad($lon_degrees);
// find the northmost, southmost, eastmost and westmost corners $distance_in_miles away
// original formula from
// http://www.movable-type.co.uk/scripts/latlong.html
$northmost  = asin(sin($lat_r) * cos($distance_in_miles/$radius) + cos($lat_r) * sin ($distance_in_miles/$radius) * cos($due_north));
$southmost  = asin(sin($lat_r) * cos($distance_in_miles/$radius) + cos($lat_r) * sin ($distance_in_miles/$radius) * cos($due_south));
$eastmost = $lon_r + atan2(sin($due_east)*sin($distance_in_miles/$radius)*cos($lat_r),cos($distance_in_miles/$radius)-sin($lat_r)*sin($lat_r));
$westmost = $lon_r + atan2(sin($due_west)*sin($distance_in_miles/$radius)*cos($lat_r),cos($distance_in_miles/$radius)-sin($lat_r)*sin($lat_r));

$northmost = rad2deg($northmost);
$southmost = rad2deg($southmost);
$eastmost = rad2deg($eastmost);
$westmost = rad2deg($westmost);

// sort the lat and long so that we can use them for a between query
if ($northmost > $southmost) {
$lat1 = $southmost;
$lat2 = $northmost;

} else {
$lat1 = $northmost;
$lat2 = $southmost;
}

if ($eastmost > $westmost) {
$lon1 = $westmost;
$lon2 = $eastmost;

} else {
$lon1 = $eastmost;
$lon2 = $westmost;
}
return array($lat1,$lat2,$lon1,$lon2);
}

function calcDistance($p1,$p2){
$R = 6371000; // m
$dLat = deg2rad($p2['lat']-$p1['lat']);
$dLon = deg2rad($p2['lng']-$p1['lng']);
$a = sin($dLat/2) * sin($dLat/2) +
cos(deg2rad($p1['lat'])) * cos(deg2rad($p2['lat'])) *
sin($dLon/2) * sin($dLon/2);
$c = 2 * atan2(sqrt($a), sqrt(1-$a));
$d = $R * $c;
return $d;
}