All of web's and excel's PivotMatrix and PivotTable widgets have a property called "emptyValue" which is default to "-". Set it to 0 like this in the excel view for your case:

//MyReportExcel.view.php
\koolreport\excel\PivotMatrix::create(array(
    ...
    "emptyValue" => 0,
));

Pls open the file koolreport/pivot/PivotUtil.php and add the following line to function computeDataCellMaps():

    protected function computeDataCellMaps()
    {
        $cMetas = $this->dataStore->meta()['columns'];
        $cellMap = Util::get($this->map, 'dataCell', function ($v, $info) use ($cMetas) {
            if (!isset($v)) return $this->emptyValue; // add this line

We will apply a fix in the next version of KoolReport. Rgds,

Sorry, pls add this line in function __construct as well:

    public function __construct(&$dataStore, $params = [])
    {
        ...
        $this->totalName = Util::get($this->params, 'totalName', 'Total');
        $this->emptyValue = Util::get($this->params, 'emptyValue', '-'); // add this line