Fatal error about JsonSerializable

Question

While I have php 5.5.3 and Joomla 3.1.5, I get this error:

Fatal error: Interface 'JsonSerializable' not found in /var/www/joomla/libraries/joomla/registry/registry.php on line 22

This is the output of php --version:

PHP 5.5.3-1ubuntu2 (cli) (built: Oct  9 2013 14:49:24) 
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2013 Zend Technologies
    with Zend OPcache v7.0.3-dev, Copyright (c) 1999-2013, by Zend Technologies

Answer 1

Are you using Ubuntu 13.10? If so, try installing the php5-json package. I guess it is perhaps new to 13.10 .

I have it and PHP v5.5.3 working fine so far. See this link for someone's blog (not mine) about installing Joomla with Ubuntu 13.10 (which has PHP v5.5.3).

Answer 2

If you have a look at the Technical requirements for Joomla 3.x, you will see that the minimum is PHP 5.3 and the recommended is 5.4.

So I would strongly recommend that you go back to PHP 5.4 as I believe there are a few known issues with PHP 5.5 and above.