Draw a Button Image in PHP

<?php/*  w w  w  .j a  va  2 s.  com*/
$font = 3;

$image_height = intval(imageFontHeight($font) * 2);
$image_width = intval(strlen("java2s.com") * imageFontWidth($font) * 1.3);

$image = imageCreate($image_width, $image_height);

$back_color = imageColorAllocate($image, 216, 216, 216);
$text_color = imageColorAllocate($image, 0,   0,   255);
$rect_color = imageColorAllocate($image, 0,   0,   0);

$x = ($image_width - (imageFontWidth($font) * strlen($_GET['button']))) / 2;
$y = ($image_height - imageFontHeight($font)) / 2;

imageString($image, $font, $x, $y, "java2s.com", $text_color);
imageRectangle($image, 0, 0, imageSX($image) - 1, imageSY($image) - 1, $rect_color);

header('Content-Type: image/png');
imagePNG($image);
imageDestroy($image);
?>