Haversine formula (PHP/MySQL)

gistfile1.aw

/**
 * Generates the string for the Haversine function. We assume that the `zipcode`, `latitude`,
 * and `longitude` columns are named accordingly. We are also not doing much error-checking
 * here; this is a simple text cruncher to make things prettier.
 * We may also be integrating some extra SQL in, passed in via the $extra parameter
 * 
 * @param   string      $table      The table to search in
 * @param   float       $lat        The latitude part of the reference coordinates
 * @param   float       $lng        The longitude part of the reference coordinates
 * @param   int         $radius     The radius to search within
 * @param   string      $extra      Some extra SQL for the city/state part of the search
 * 
 * @return  string      Returns an SQL query as a string
 *
**/
    private function _haversine_sql($table,$lat,$lng,$radius,$extra = '') {
        $output  = "SELECT distinct *, 
                    ( 3959 * acos( cos( radians( {$lat} ) ) * cos( radians( `latitude` ) ) * cos( radians( `longitude` ) - radians( {$lng} ) ) + sin( radians( {$lat} ) ) * sin( radians( `latitude` ) ) ) ) AS distance
                    FROM `{$table}` HAVING distance <= {$radius} {$extra}
                    ORDER BY distance;";
        return $output;
        } // end _haversine_sql($table,$lat,$lng,$radius,$extra = '')