src/Auth/ApplicationOnlyAuth.php
protected function buildRequestHeader()
    {
        $bearerToken = $this->bearerToken;

        if ($this->bearerToken === null) {
            $bearerToken = $this->getBearerToken();
        }

        return array(
            'Authorization: Bearer ' . rawurlencode($bearerToken),
            'Expect:'
        );
    }
protected function buildRequestHeader()
    {
        $bearerToken = $this->bearerToken;

        if ($this->bearerToken === null) {
            $bearerToken = $this->getBearerToken();
        }

        return array(
            'Authorization: Bearer ' . rawurlencode($bearerToken),
            'Expect:'
        );
    }
Building request HTTP headers

@return array  HTTP headers