imagettftext

Например так

header ("Content-type: image/png");
$im = @imagecreate (180, 20)
or die ("Cannot Initialize new GD image stream");
$background_color = imagecolorallocate ($im, 200, 200, 200);
$text_color = imagecolorallocate ($im, 255, 255, 255);
$text="Text";
imagestring ($im, 3, 0, 0, $text, $text_color);
$img=imagepng ($im);