Something

$img	= imagecreatetruecolor(140, 50);
$black	= imagecolorallocate($img, 8, 8, 8);

$color[]	= imagecolorallocate($img, 255, 48, 0);
$color[]	= imagecolorallocate($img, 255, 114, 0);
$color[]	= imagecolorallocate($img, 254, 105, 66);
$color[]	= imagecolorallocate($img, 255, 168, 0);
$color[]	= imagecolorallocate($img, 255, 255, 255);

shuffle($color);
imagefilledrectangle($img, 0, 0, 140, 50, $black);
imagecolortransparent($img, $black);

$string = 'asdfgqweryxcvtzuvbnmghjkp123456789';
$pocet	= strlen($string);
$x		= 20;
$cely	= '';
for($prubeh = 0; $prubeh < 5; $prubeh++)
{
	$cely .= $znak = strtoupper($string[rand(0, $pocet-1)]);
	imagettftext($img, 20, rand(-30, 30), $x += 17, 30, $color[$prubeh], './tahoma.ttf', $znak);
}

header("Content-type: image/png");
imagepng($img);
imagedestroy($img);