(PECL sphinx >= 0.1.0)
SphinxClient::setGeoAnchor — Set anchor point for a geosphere distance calculations
$attrlat
   , string $attrlong
   , float $latitude
   , float $longitude
   )Sets anchor point for a geosphere distance (geodistance) calculations and enables them.
Once an anchor point is set, you can use magic "@geodist" attribute name in your filters and/or sorting expressions.
attrlatName of a latitude attribute.
attrlongName of a longitude attribute.
latitudeAnchor latitude in radians.
longitudeAnchor longitude in radians.
   Returns TRUE on success or FALSE on failure.