final protected function auth($string = '') {
    $canonical = strtoupper($this->method) . $this->path() . strval($this->datetime) . $string;
    $signature = $this->hhmac($canonical, $this->api_key_secret);
    return sprintf('HHMAC; key=%s; signature=%s; date=%s',
      $this->api_key_id, $signature,
      $this->datetime
    );
  }
final protected function auth($string = '') {
    $canonical = strtoupper($this->method) . $this->path() . strval($this->datetime) . $string;
    $signature = $this->hhmac($canonical, $this->api_key_secret);
    return sprintf('HHMAC; key=%s; signature=%s; date=%s',
      $this->api_key_id, $signature,
      $this->datetime
    );
  }
final protected function auth ( $ string = '' ) { $ canonical = strtoupper ( $ this -> method ) . $ this -> path ( ) . strval ( $ this -> datetime ) . $ string ; $ signature = $ this -> hhmac ( $ canonical , $ this -> api_key_secret ) ; return sprintf ( 'HHMAC; key=%s; signature=%s; date=%s' , $ this -> api_key_id , $ signature , $ this -> datetime ) ; }
Create canonical version of the request as a byte-wise concatenation.

@param (string) $string String to concatenate (see POST method).

@return (string) HMAC cryptographic hash
Create canonical version of the request as a byte - wise concatenation .