<?php
// Create a 300x100 image
$im = imagecreate(300, 100);
// Set the background to be red
imagecolorallocate($im, 255, 0, 0);
// Get the color index for the background
$bg = imagecolorat($im, 0, 0);
// Set the backgrund to be blue
imagecolorset($im, $bg, 0, 0, 255);
// Output the image to the browser
header('Content-Type: image/png');
imagepng($im);
imagedestroy($im);
?>