ถามเรื่อง JP กราฟ หน่อยครับ พอ Run เเล้ว error ครับ unknow font font family specification

<?php  
require("../jpgraph.php"); //this is path of tool 
require("../jpgraph_bar.php"); 
require("../jpgraph_flags.php");
include ("connect.php") ; 
$sql1 = "select * from tb_year ";  
$result = mysql_query($sql1) 
or die("query error 1 ".mysql_error());  
$sumtotal = 0; 
 
 
while ($rs = mysql_fetch_array($result)){   
$xdata[] = $rs["name_year"]; 
$ydata[] = $rs["total_year"]; 
 
 
} 

 
$graph = new Graph(350,450); 
$graph->SetScale("textlin"); 
$graph->SetMarginColor('white'); 
$graph->SetBackgroundGradient("white","whitesmoke",GRAD_HOR, BGRAD_MARGIN); 
$graph->SetShadow(); 
$graph->SetMargin(40,30,20,40); 
 
 
 
 
$graph->title->SetFont(FF_TAHOMA, FS_BOLD,12); 
$graph->title->Set(iconv('TIS-620','UTF-8',"รายงาน")); 
$graph->subtitle->SetFont(FF_TAHOMA, FS_BOLD,12); 
$graph->subtitle->Set(iconv('TIS-620','UTF-8',"รายงานลูกค้า")); 
 
 
$graph->xaxis->title->Set("name_year"); 
$graph->yaxis->title->Set("Bath"); 
$graph->xaxis->SetTickLabels($xdata); 
$graph->SetMarginColor('white'); 
$graph->SetBackgroundGradient("white","whitesmoke",GRAD_HOR, BGRAD_MARGIN); 
 
 
$bplot = new BarPlot($ydata); 
$bplot->SetFillGradient('white','pink',GRAD_VERT); 
$bplot->SetColor('gainsboro'); 
$bplot->SetWeight(1); 
$bplot->value->Show(); 
$bplot->value->SetFont(FF_TAHOMA, FS_BOLD,8); 
$bplot->value->SetAngle(45); 

 
$graph->Add($bplot); 
 
 
$graph->Stroke(); 
?>