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
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).