Error T_CONSTANT_ENCAPSED_STRING?

I want to update and send me this error

  

Error T_CONSTANT_ENCAPSED_STRING

What did I do wrong? I've spent hours looking for the error.

case "list":
            $query_Tipo = $objArticulo->Listar();
            $data = Array();
            $i = 1;
            while ($reg = $query_Tipo->fetch_object()) {

                $data[] = array("id"=>$i,
                    "1"=>$reg->categoria,
                    "2"=>$reg->unidadMedida,
                    "3"=>$reg->nombre,
                    "4"=>$reg->descripcion,
                    "5"=>'<img width=100px height=100px src="./'.$reg->imagen.'" />',
                    '<button class="btn btn-warning" data-toggle="tooltip" title="Editar" onclick="cargarDataArticulo('.$reg->idarticulo.',\''.$reg->idcategoria.'\',\''.$reg->idunidad_medida.'\',\''.$reg->nombre.'\',\''.$reg->descripcion.'\',\''.$reg->imagen.'\')"><i class="fa fa-pencil"></i> </button>&nbsp;'.
                    '<button class="btn btn-danger" data-toggle="tooltip" title="Eliminar" onclick="eliminarArticulo('.$reg->idarticulo.')"><i class="fa fa-trash"></i> </button>');
                $i++;
            }
            $results = array(
            "sEcho" => 1,
            "iTotalRecords" => count($data),
            "iTotalDisplayRecords" => count($data),
            "aaData"=>$data);
            echo json_encode($results);


            //$str = $nombre;
            //echo stripslashes($str);
            //echo addslashes($str);

            break;