public function has(string $name) : bool
  {
    if (isset($this->all[$name])) return true;
    return false;
  }
public function has(string $name) : bool
  {
    if (isset($this->all[$name])) return true;
    return false;
  }
public function has ( string $ name ) : bool { if ( isset ( $ this -> all [ $ name ] ) ) return true ; return false ; }
Check if header is present

@param string $name
@return bool
Check if header is present