//query
$query = "SELECT DISTINCT toponimia, k_n_rua AS id, ST_AsGeoJson(ST_Transform(the_geom,900913)) AS GeoJson
     FROM ruas
     WHERE toponimia IS NOT NULL";

//execute query
 $resultado = pg_query($conexao,$query);

//print
print '{"rows" : ' . json_encode(array_values(pg_fetch_all($resultado))) . '}';