Query a layer in mapscript php

When learning to use mapserver and mapscript, the first steps have been to display, zoom and pan. Zooming and panning is quite easy, it is just a line like

$map->zoompoint($zoomfactor,$clickpoint,$map->width,$map->height,$mapextent);
where $map is a mapboject, $zoomfactor is a number telling how many times to zoom in or out, positive for zoom in, negative for zoom out, $clickpoint is a pointobject of the location of the click in image coordinates.

Then enter the urge to do a query as well – but not much luck. I reused the same $clickpoint and tried
$map->queryByPoint($clickpoint, MS_SINGLE, 1);
(after doing some adjustments in the map file) but to no luck. Digging into the kmap source code, I understood after a while that the coordinates needed to be in map coordinates and not image coordinates. That is just a simple linear transformation, just with the little snag that the y-coordinates go the opposite direction in the image than in the map. Kmap called the transformation function twice, once for each koordinate, I preferred to make one function for the two-dimentional transformation:

function pix2geo($mapx,$mapy,$minx,$miny,$maxx,$maxy,$sizex,$sizey)
					 
// $mapx and $mapy: image coordinates of point of interest 				 
// $minx, $maxx,$miny, $maxy map extent in map coordinates
// $sizex and $sizey, width and height of image
{	
	list($miny,$maxy)=array($maxy,$miny); 
	// swaps miny and max y since the coordinates acsends upwards in the map, downwards in the picture
	$geopoint=array();
	foreach( array('x','y') as $dim){
		$p=array();
		foreach(array('map','min','max','size') as $par){
			$name="$par$dim";
			$p[$par]=$$name;
		}
		$geowidth=$p['max']-$p['min'];
		$geopoint[$dim]=$p['map']/$p['size']*$geowidth+$p['min'];
	}
	return(array($geopoint['x'],$geopoint['y']));
}

This can be used like:

list($geoX,$geoY)=pix2geo($_GET['MAP_x']*1,$_GET['MAP_y']*1,$minx,$miny,$maxx,$maxy,$map->width,$map->height);
$geopoint=ms_newpointObj();
$geopoint->setXY( $geoX,$geoY);
$map->queryByPoint($geopoint, MS_SINGLE, 1);

followed by getNumResults for each layer, getResult, getShape and finally getting the relevant values out of the shape.

I have to admit, I simplified things a bit at the beginning. The point needs to be in the projection of the queried data set. As I have the queried dataset in geographical projection and want to have the map in utm, I still have a problem there..