self.code()

function _encode_query($s) {
  $s = str_replace(',', urlencode(','), $s);
  $s = str_replace(':', urlencode(':'), $s);
  $s = str_replace(';', urlencode(';'), $s);
  return $s;
}
 
function _encode_signature($s) {
  $s = str_replace('+', urlencode('+'), $s);
  $s = str_replace('=', urlencode('='), $s);
  return $s;
}
 
function fetch($power_query, $access_key_id, $associate_tag) {
  $url_base = 'http://webservices.amazon.com/onca/xml?';
  $url_params = array(
    'Operation' => 'ItemSearch',
    'Service' => 'AWSECommerceService',
    'AWSAccessKeyId' => $access_key_id,
    'Version' => '2009-01-06',
    'Sort' => 'salesrank',
    'ResponseGroup' => 'ItemAttributes,Images',
    'SearchIndex' => 'Books',
    'Power' => $power_query,
    'Availability' => 'Available',
    'Condition' => 'All',
    'Timestamp' => gmdate('Y-m-d\TH:i:s\Z')
  );
  $pairs = array();
  foreach($url_params as $k => $v) {
    $pairs[] = $k.'='.$this->_encode_query($v);
  }
  sort($pairs);
  $canonical = implode('&', $pairs);
  $base = 'GET'.PHP_EOL.'webservices.amazon.com'.PHP_EOL.'/onca/xml'.PHP_EOL;
  $to_sign = $base.$canonical;
  $signature = base64_encode(hash_hmac('sha256', $to_sign, $associate_tag, true));
  $signature = $this->_encode_signature($signature);
  $request = $url_base.$canonical.'&Signature='.$signature;
  $response = file_get_contents($request);
  $xml = simplexml_load_string($response);
  if (!is_object($xml)) {
    return null;
  } else {
    $products = array();
    if (sizeof($xml->Items->Item) > 0) {
      foreach($xml->Items->Item as $item) {
        $products[] = $item;
      }
    }
    return $products;
  }
}

function get_gradient($hex_from, $hex_to, $color_steps) {
  $from_rgb = array(
    'r' => hexdec(substr($hex_from, 0, 2)),
    'g' => hexdec(substr($hex_from, 2, 2)),
    'b' => hexdec(substr($hex_from, 4, 2))
  );
  $to_rgb = array(
    'r' => hexdec(substr($hex_to, 0, 2)),
    'g' => hexdec(substr($hex_to, 2, 2)),
    'b' => hexdec(substr($hex_to, 4, 2))
  );
  $step_rgb = array(
    'r' => ($from_rgb['r'] - $to_rgb['r']) / ($color_steps - 1),
    'g' => ($from_rgb['g'] - $to_rgb['g']) / ($color_steps - 1),
    'b' => ($from_rgb['b'] - $to_rgb['b']) / ($color_steps - 1)
  );
  $gradient_colors = array();
  for($i = 0; $i < $color_steps; $i++) {
    $rgb = array(
      'r' => floor($from_rgb['r'] - ($step_rgb['r'] * $i)),
      'g' => floor($from_rgb['g'] - ($step_rgb['g'] * $i)),
      'b' => floor($from_rgb['b'] - ($step_rgb['b'] * $i))
    );
    $hex_rgb = array(
      'r' => sprintf('%02x', ($rgb['r'])),
      'g' => sprintf('%02x', ($rgb['g'])),
      'b' => sprintf('%02x', ($rgb['b']))
    );
    $gradient_colors[] = implode(null, $hex_rgb);
  }
  return $gradient_colors;
}

get_gradient('#0084b4', '#a9e0f4', 10);
 
(
    [0] => 0084b4
    [1] => 128ebb
    [2] => 2598c2
    [3] => 38a2c9
    [4] => 4bacd0
    [5] => 5db7d7
    [6] => 70c1de
    [7] => 83cbe5
    [8] => 96d5ec
    [9] => a9e0f4
)