src/Request.php
public function getHeader($key, $default = false)
    {
        return $this->headers->has($key) ? $this->headers->get($key) : $default;
    }
public function getHeader($key, $default = false)
    {
        return $this->headers->has($key) ? $this->headers->get($key) : $default;
    }
public function getHeader ( $ key , $ default = false ) { return $ this -> headers -> has ( $ key ) ? $ this -> headers -> get ( $ key ) : $ default ; }
Get specific header.

@param $key
@param bool $default

@return bool|string|string[]
Get specific header .