nearest geographical feature to a point?

[Miguel Gonçalves]

Hi,

I am building an application using the MapServer.
I have a map with several layers of points, lines and polygons.
When I perform a request to my application, I give it a point in the 
form (latitude,longitude) and I want to obtain the maximum geographical 
information of the layers for thr the given point.

I am using the WFS interface and the GetFeature request.
My problem is very simple. Supose that I have a point layer cities in my 
map and I have the city X in the point (a,b).
If the point that I give in the GetFeature request is (a,b) I will 
obtain the geographical information for the city X.
The real problem arises if I pass in the GetFeature request a point that 
does not coincides with any location in the map.
Supose that I pass the point (a,b+0.0001). This point is really near the 
city X but I will not obtain any information in the WFS request.
It woul be wounderfull if I could have a kind of WFS request that could 
give me the nearest city in a certain range of the point.

I know that I can use the bounding box  in the WFS GetCapabilities 
request to give me the cities near the point but,
bounding box is a rectangle.
I would prefer to have a proximity range.
But even better than having the geographical features inside a given 
range I would like to have the nearest feature to a given point.
Does anybody knows how to get the nearest feature to a certain given 
point using the MapServer?
Is it possible in WFS?
Thanks and best regards.

Miguel