I have already GD2 + Freetype2 installed in my machine

when i try to use the imagettfbbox() function , it's show that php cannot fine the required library for that function !! however when i used other image function , it's work fine with me ??

============ short script the reproduces the problem ======
<?php 

$imagewidth = 100; 
$imageheight = 20; 
$fontsize = 12; 
$myimg=ImageCreate($imagewidth, $imageheight); 
$col1=ImageColorAllocate($myimg, 255, 0, 0); 
$col2=ImageColorAllocate($myimg, 255, 255, 255); 
$thetextbox = ImageTTFBBox ($fontsize, 0, "TIMES.TTF", "My Button"); 
$textwidth = (($thetextbox[4] + $thetextbox[2]) / 2) - (($thetextbox[6] + $thetextbox[0]) / 2); 
$xpos = ($imagewidth - $textwidth) / 2; 
$ypos = 14; 
ImageTTFText ($myimg, $fontsize, 0, $xpos, $ypos, $col2, "./ttfonts/arialnb.ttf", "My Button"); 
ImagePNG($myimg, "myimg.png"); 
ImageDestroy($myimg); 
?> 
<img src="myimg.png" border=0>
================================================


any suggestions ??


Regards,
AlNadabi