PHP pChart used with XMAPP - retrieve Stroke image from HTML

Question

i am trying to create a chart in PHP through pChart 2.3 class. My doubt is on this function:

    function autoOutput(string $FileName = "output.png", int $Compression = 6, $Filters = PNG_NO_FILTER)
    {
        if (php_sapi_name() == "cli") {
            $this->Render($FileName, $Compression, $Filters);
        } else {
            $this->Stroke(TRUE, $Compression, $Filters);
        }
    }

Html Code:

<div id="filtri"> 
<?php include($_SERVER['DOCUMENT_ROOT'] . "/reportingBug/generaGrafico1.php");?>
<?php include($_SERVER['DOCUMENT_ROOT'] . "/reportingBug/recuperaTempiMediLavBug.php");?>
<?php include($_SERVER['DOCUMENT_ROOT'] . "/reportingBug/recuperaTempiMediBug.php");?>
<img src="temp/example.drawBarChart.spacing.png">
</div>

Php Script:

/* Render the picture (choose the best way) */
$myPicture->autoOutput("temp/example.drawBarChart.spacing.png");

?>

If i force the code in order to follow the if branch with Render function everything is working right
because it creates a PNG image in root folder and i can retrieve it from HTML.

but it goes through the else branch, so the stroke function is called.

In the case, i have two problems:

1. i don't know how to retrieve the PNG from HTML
2. i have a problem because the browser shows following:

I tried to use a phisical image (PNG file create on the server folder) but i think it's not correct because many user will access the application concurrently.