Amazon S3 Expiring Link

I was working on Amazon S3 Cloud HTML5 MP3 Player for S3 Bucket security and Expiring Media links.

<?php
  if(!function_exists('el_crypto_hmacSHA1')){
      /**
      * Calculate the HMAC SHA1 hash of a string.
      *
      * @param string $key The key to hash against
      * @param string $data The data to hash
      * @param int $blocksize Optional blocksize
      * @return string HMAC SHA1
      */
      function el_crypto_hmacSHA1($key,$data,$blocksize=64){
          if(strlen($key)>$blocksize)$key=pack('H*',sha1($key));
          $key=str_pad($key,$blocksize,chr(0x00));
          $ipad=str_repeat(chr(0x36),$blocksize);
          $opad=str_repeat(chr(0x5c),$blocksize);
          $hmac=pack('H*',sha1(
              ($key^$opad).pack('H*',sha1(
                  ($key^$ipad).$data
              ))
          ));
          returnbase64_encode($hmac);
      }
  }
  if(!function_exists('el_s3_getTemporaryLink')){
      /**
      * Create temporary URLs to your protected Amazon S3 files.
      *
      * @param string $accessKey Your Amazon S3 access key
      * @param string $secretKey Your Amazon S3 secret key
      * @param string $bucket The bucket (bucket.s3.amazonaws.com)
      * @param string $path The target file path
      * @param int $expires In minutes
      * @return string Temporary Amazon S3 URL
      * @see http://awsdocs.s3.amazonaws.com/S3/20060301/s3-dg-20060301.pdf
      */
      function el_s3_getTemporaryLink($accessKey,$secretKey,$bucket,$path,$expires=5){
          // Calculate expiry time
          $expires=time()+intval(floatval($expires)*60);
          // Fix the path; encode and sanitize
          $path=str_replace('%2F','/',rawurlencode($path=ltrim($path,'/')));
          // Path for signature starts with the bucket
          $signpath='/'.$bucket.'/'.$path;
          // S3 friendly string to sign
          $signsz=implode("\n",$pieces=array('GET',null,null,$expires,$signpath));
          // Calculate the hash
          $signature= el_crypto_hmacSHA1($secretKey,$signsz);
          // Glue the URL ...
          $url=sprintf('http://%s.s3.amazonaws.com/%s',$bucket,$path);
          // ... to the query string ...
          $qs=http_build_query($pieces=array(
              'AWSAccessKeyId'=>$accessKey,
              'Expires'=>$expires,
              'Signature'=>$signature,
          ));a
          // ... and return the URL!
          return$url.'?'.$qs;
      }
  }
  ?>

Uses:

$ExpiringLink = el_s3_getTemporaryLink(‘AWS-KEY’, ‘AWS-SECRET-KEY’, ‘BUCKET’, ‘FILENAME’, ‘EXPIRING-TIME’);

Demo Amazon S3 Cloud HTML5 MP3 Player

Reference: http://snipplr.com/view/46753.57507/