<?PHP
 
HEADER("Content-type: image/png");
 
$height = 100;
$width = 50;
 
$start = '000000';
$end = 'FFFFFF';
IF ($_GET["start"]) {
  $start = $_GET["start"];
}
IF ($_GET["end"]) {
  $end = $_GET["end"];
}
 
$start_r = HEXDEC(SUBSTR($start, 0, 2));
$start_g = HEXDEC(SUBSTR($start, 2, 2));
$start_b = HEXDEC(SUBSTR($start, 4, 2));
$end_r = HEXDEC(SUBSTR($end, 0, 2));
$end_g = HEXDEC(SUBSTR($end, 2, 2));
$end_b = HEXDEC(SUBSTR($end, 4, 2));
$image = @imagecreate($width, $height);
 
FOR($y=0;$y<$height;$y++) {
  FOR($x=0;$x<$width;$x++) {
    IF ($start_r == $end_r) {
      $new_r = $start_r;
    }
    $difference = $start_r - $end_r;
    $new_r = $start_r - INTVAL(($difference / $height) * $y); 
    IF ($start_g == $end_g) {
      $new_g = $start_g;
    }
    $difference = $start_g - $end_g;
    $new_g = $start_g - INTVAL(($difference / $height) * $y);         
    IF ($start_b == $end_b) {
      $new_b = $start_b;
    }
    $difference = $start_b - $end_b;
    $new_b = $start_b - INTVAL(($difference / $height) * $y);
    $row_color = imagecolorresolve($image, $new_r, $new_g, $new_b);
    imagesetpixel($image, $x, $y, $row_color);
  }    
}
 
imagepng($image);
imagedestroy($image);
 
 
// Example usage: 
// <img src="gradient.php?start=START_HEX_COLOR&end=END_HEX_COLOR" />
 
 
?>