/**
* Converts and signs a PHP object or array into a JWT string.
*
* @param object|array $payload PHP object or array
* @param string $key The secret key
* @param string $algo The signing algorithm. Supported
* algorithms are 'HS256', 'HS384' and 'HS512'
*
* @return string A signed JWT
* @uses jsonEncode
* @uses urlsafeB64Encode
*/
public static function encode($payload, $key, $algo = 'HS256')
{
$header = array('typ' => 'JWT', 'alg' => $algo);
$header_en = JWT::base64url_encode(JWT::jsonEncode($header));
$payload_en = JWT::base64url_encode(JWT::jsonEncode($payload));
$segments = array();
$segments[] = JWT::base64url_encode(JWT::jsonEncode($header));
$segments[] = JWT::base64url_encode(JWT::jsonEncode($payload));
$signing_input = implode('.', $segments);
$signature = JWT::sign($signing_input, $key, $algo);
$segments[] = JWT::base64url_encode($signature);
return implode('.', $segments);
}