Estoy tratando de guardar el gráfico circular como un archivo pdf como enhttp://keepcoding.ehsanabbasi.com/php/convert-google-chart-to-png-and-pdf/ Tener javascript dentro de php.chartsrc muestra el siguiente valor en lugar de la fuente de imagen png

"function (){if(!this.b||!this.$||!this.Ua)throw m("Chart has not finished drawing.");var a=new Ql(this.V,this.Aa),b=Tl(this.ma)[Wb](ih),a=YO(b,a),a=new EO(b,a),c=new RO(b),a=this.sO(c,a),c=yY(this.ig,this.$,this.Ua);a.Lp(this.$,c);return b[cc][0].toDataURL(Ssa)} failed (filesystem path '/var/www/html/function (){if(!this.b||!this.$||!this.Ua)throw m("Chart has not finished drawing.");var a=new Ql(this.V,this.Aa),b=Tl(this.ma)[Wb](ih),a=YO(b,a),a=new EO(b,a),c=new RO(b),a=this.sO(c,a),c=yY(this.ig,this.$,this.Ua);a.Lp(this.$,c);return b[cc][0].toDataURL(Ssa)}')"

 $script ="

        google.setOnLoadCallback(drawChart);
        function drawChart() { //code for drawing chart}
        var chart = new google.visualization.PieChart(document.getElementById('piechart'));

        google.visualization.events.addListener(chart, 'ready', function ()      {
        var chartsrc = chart.getImageURI();
     });

      $doc->addScriptDeclaration($script);
      echo "<div id='piechart'></div>";