Geojson in postgis Geometry : Z dimension error

i had this php code :

$geom1='{"type":"Feature","geometry":{"type":"Polygon","coordinates":[[[-32514.400906806848,4810093.013501738],[-32877.47679116143,4809500.626532529],[-34473.099756614494,4810026.131101989],[-33412.535989157666,4811124.913383588],[-32514.400906806848,4810093.013501738]]]},"properties":null}';
$geom_poly=explode('Polygon',$geom1);
$geom_def=$geom_poly[0]."MultiPolygon".$geom_poly[1];
$geom2=explode('{',$geom_def);
$geom3=explode('}',$geom2[2]);
$CRS='"crs":{"type":"name","properties":{"name":"EPSG:3857"}}';
$geometria1=$geom3[0];
$geom4='{'.$geometria1.'},'.$CRS;





$uso_edit = $_POST['uso'];
$afeccion_edit = $_POST['afeccion'];
$retablo_edit = $_POST['retablo'];
$proteccion_edit = $_POST['proteccion'];
$altura_edit = $_POST['altura'];
$query = "INSERT INTO prueba(geom,prueba) VALUES  ( ST_SetSRID(ST_GeomFromGeoJSON('".$geom4."'),3857) , 'jsadfjlasd') ";

pg_exec($query); 

I had this error :

pg_exec(): Query failed: ERROR: Geometry has Z dimension but column does not in

My PostgreSQL version is 9.4: and my table code is :

CREATE TABLE prueba
(
   id_0 serial NOT NULL,
   geom geometry(MultiPolygon,3857),
   id integer,

   prueba character varying(80),
   CONSTRAINT prueba_pkey PRIMARY KEY (id_0)
 )
 WITH (
 OIDS=FALSE
 );
 ALTER TABLE prueba
 OWNER TO postgres;

I try change the dimension with :

ALTER TABLE urbana_prueba  
ALTER COLUMN geom TYPE geometry(MultiPolygon, 3857) 
USING ST_Force_3D(geom);

but dosen't work......

Answer

You were almost there...

MultiPolygonZ should do the trick:

ALTER TABLE urbana_prueba  
ALTER COLUMN geom TYPE geometry(MultiPolygonZ, 3857) 

USING ST_Force_3D(geom);