I'm trying to setup exporting to PDF via Chrome Headless, but I'm getting the following PHP exception:

Fatal error: Uncaught RuntimeException: Directory name must not be empty. in C:\wamp64\www\LegalBillingAPI\koolreport\cloudexport\vendor\chromeheadlessio\php-client\src\Exporter.php on line 46

Here are the files I created for this report...

index.php

<?php 

require_once "MatterTotalsByAccount.php";
$mattertotalsbyaccount = new MatterTotalsByAccount;

$mattertotalsbyaccount
    ->cloudExport("MatterTotalsByAccount")
    ->chromeHeadlessio("my token")
    ->pdf(array(
        "format"=>"A4",
        "landscape"=>false
    ))
    ->toBrowser("MatterTotalsByAccount.pdf");

MatterTotalsByAccount

<?php

// Require autoload.php from koolreport library
require_once "../../koolreport/core/autoload.php";

//Specify some data processes that will be used to process
use \koolreport\processes\Group;
use \koolreport\processes\Sort;
use \koolreport\processes\Limit;

//Define the class
class MatterTotalsByAccount extends \koolreport\KoolReport
{
    use \koolreport\cloudexport\Exportable;

    protected function settings()
    {
        //Define the "matter_totals_by_account" data source which is the result of the MySQL Stored Procedure 
        return array(
            "dataSources"=>array(
                "matter_totals_by_account"=>array(
                    'host' => 'localhost',
                    'username' => 'root',
                    'password' => '',
                    'dbname' => 'databasename',
                    'charset' => 'utf8',  
                    'class' => "\koolreport\datasources\MySQLDataSource"  
                ),
            )
        );
    }
  
    protected function setup()
    {
        $this->src('matter_totals_by_account')
        ->query("CALL MatterTotalsByAccount('2019-01-01','2019-12-31')")
        //Select the data source then pipe data through various process
        //until it reach the end which is the dataStore named "sales_by_customer".
        ->pipe(new Group(array(
            "by"=>array("accountName","matter"),
            "sum"=>"total"
        )))
        ->pipe(new Sort(array(
            "accountName","matter"=>"asc"
        )))
        //->pipe(new Limit(array(10)))
        ->pipe($this->dataStore('totals_by_matter_and_account'));
    }
}

MatterTotalsByAccount.view.php

<?php 
    use \koolreport\widgets\koolphp\Table;
?>

<div class="report-content">
    <div class="text-center">
        <h1>Legal Fees Paid: xx/xx/xxxx to xx/xx/xxxx</h1>
        <p class="lead">Sorted by Account Name, Matter</p>
    </div>

    <?php
    ?>
    <?php
    Table::create(array(
        "dataStore"=>$this->dataStore('totals_by_matter_and_account'),
            "grouping"=>array(
                "accountName"=>array(
                    "calculate"=>array(
                        "{sumAmount}"=>array("sum","total")
                    ),
                    "top"=>"<b>{accountName}</b>",
                    "bottom"=>"<td align='right'><b>Total:</b></td><td align='right'><b>{sumAmount}</b></td>",
                    //"bottom"=>"<td><b>{accountName} TOTAL:</b></td><td><b>{sumAmount}</b></td>",
                ),
            ),
            "sorting"=>array(
                "matter"=>"asc"
            ),
            "showHeader"=>false,
            "showFooter"=>true,
            "columns"=>array(
                /*
                "accountName"=>array(
                    "label"=>"Account",
                ),
                */
                "matter"=>array(
                    "label"=>"Matter",
                    "cssStyle"=>"padding-left: 50px"
                ),
                "total"=>array(
                    "type"=>"number",
                    "label"=>"Total",
                    "prefix"=>"$",
                    "decimals"=>2,
                    "cssStyle"=>"text-align:right",
                    "footer"=>"sum",
                    "footerText" =>"<b><i>TOTAL FEES PAID</i></b>: <b>@value</b>"
                )
            ),
        "cssClass"=>array(
            "table"=>"table table-hover table-bordered"
        )
    ));
    ?>
</div>

Hi David, that took away my error, thank you! However, one more small thing - instead of the PDF displaying in a browser window (as it used to before I started receiving that error), it now just shows a Save dialog to save the PDF to my local PC. Is there a way to have the rendered PDF display in the browser window? Again, it used to do this, prior to me receiving that error you just helped with.

Also, I notice the tmp folder that's created is never automatically deleted/removed - is that the intention?

Nevermind the above - I updated user permissions and all is well again. Thank you for the help!