mPDF中的SVG编码

I have a problem with UTF-8 encoding of dynamically created SVG in mPDF file. The characters of Latin Extended-A don't shows correctly. Code:

    <?php
function svg () {
    $content = '<svg>
    <rect x="5" y="10" width="830" height="25" style="fill:rgb(240,240,240)"/>
    <line x1="5" y1="35" x2="835" y2="35" style="stroke:rgb(0,0,0);stroke-width:0.5" />
    <text x="210" y="25" fill="black" font-size="10">začátek</text>
    <text x="274" y="25" fill="black" font-size="10">konec</text>
    <text x="10" y="10" fill="black" font-size="14">ěščřžýáíéůú</text>
    </svg>
    ';
    $content = iconv('UTF-8', 'UTF-8', $content);
    return $content;
}
include("../libs/mPDF/mpdf.php");
$mpdf=new mPDF('utf-8','A4',9,'arial',15,10,22,35,10,15);
$mpdf->allow_charset_conversion=true;
$mpdf->charset_in='utf-8';
$mpdf->mirrorMargins = 0;
$mpdf->WriteHTML(svg ());
$mpdf->Output(matomas_.$nazev_postu._.date('d-m-Y').".pdf",I);
exit; 
?>

Link to final PDF HERE .