code: public function getBlob($containerName = '', $blobName = '', $localFileName = '', $snapshotId = null, $leaseId = null, $additionalHeaders = array())
      {
          Assertion::notEmpty($containerName, 'Container name is not specified');
          self::assertValidContainerName($containerName);
          Assertion::notEmpty($blobName, 'Blob name is not specified.');
          Assertion::notEmpty($localFileName, 'Local file name is not specified.');
  
          file_put_contents($localFileName, $this->getBlobData($containerName, $blobName, $snapshotId, $leaseId, $additionalHeaders));
      }
docs: Get blob
  
  @param string $containerName      Container name
  @param string $blobName           Blob name
  @param string $localFileName      Local file name to store downloaded blob
  @param string $snapshotId         Snapshot identifier
  @param string $leaseId            Lease identifier
  @param array  $additionalHeaders  Additional headers. See http://msdn.microsoft.com/en-us/library/dd179371.aspx for more information.
  @throws BlobException