Dipole Consulting SPRL

php/mapscript allows to use mapserver very efficiently inside a php application.

Some parts of the behaviour is still a bit undocumented.

Querying dynamically created point layer is one of those missing parts.

This article is based on MapServer version 4.10 

To be able to query a dynamic layer, you need to have a layer definition in your mapfile.

This definition MUST have a TEMPLATE attribute (either if it points on nothing).

The following example should work :

    LAYER

        NAME "my_layer"

        STATUS ON 

        TYPE POINT

        TOLERANCE 10

        LABELCACHE ON

        LABELMAXSCALE 400000  

        TRANSPARENCY ALPHA

        TEMPLATE nofile.html

        CLASS

            NAME "Points"

            COLOR 255 0 0

            OUTLINECOLOR 255 0 0 

            SIZE 10 

            SYMBOL "circle"

            LABEL

                POSITION AUTO

                ANGLE AUTO

                SIZE 12

                COLOR 0 0 0 

                TYPE truetype

                FONT DejaVuSans

                ANTIALIAS true

                OUTLINECOLOR 255 255 255

                PARTIALS false

                ENCODING 'utf8'

            END          

        END 

        PROJECTION

            "+proj=lcc +lat_1=51.16666723333333 +lat_2=49.8333339 +lat_0=90 +lon_0=4.367486666666666 

               +x_0=150000.013 +y_0=5400088.438 +ellps=intl +units=m +no_defs"

        END       

    END

Then you need to fill in your layer with points. This is a bit tricky because you cannot add pointObj to mapeserver shapeObj.

Thus, you need to add a lineObj composed by only one point ;-) :

    $shp = ms_newShapeObj(MS_SHAPE_POINT);

    $pt = ms_newLineObj();

    $pt->addXY($point->x,$point->y);

    $shp->add($pt);

    $shp->set('classindex', $obj->get_classindex());

    $shp->set('text', $obj->get_id());

    $shp->set('index', $obj->get_internal_id());

    $lyr->addFeature($shp);

Finally, you can query your layer using a geographical point (not a pixel one !) :

    // transform pixel to geo coords :
    $cx = Pix2Geo($_POST["mapa_x"], 0, $map->height, $map_extent[0], $map_extent[2], 0);
    $cy = Pix2Geo($_POST["mapa_y"], 0, $map->width , $map_extent[1], $map_extent[3], 1);
    $mpoint = ms_newPointObj();
    $mpoint->SetXY($cx, $cy);
    // find into layer the most closed point
    $layer->set("toleranceunits",MS_METERS);
    $res = $layer->queryByPoint($mpoint, MS_SINGLE, 100);
    if ($res == MS_SUCCESS){
        $layer->open();
        $rslt  =  $layer->getResult(0);

        echo "Foudn point $rslt->shapeindex";   

    } else {

        echo "No point found"; 

     }

 ! You cannot use the $layer->getShape() method on dynamically created layer.

The key to solve this problem is to use the index of the shapeObj as key to find out which point has been selected.