I'm using Zenphoto 1.4.8 with nginx 1.9.1, mysql 5.6.25, PHP 5.6.9 (running as php-fpm server), linux 2.6.31.8.
I get the error: "cannot redeclare class Mutex".
What should I do ?

zenphoto-1.4.8/zp-core/functions-basic.php:1581:class Mutex {

Zenphoto has only that one instance of the class Mutex in functions-basic.php. You basically need to find out where you have a class with that name already declared.

It seems there can be a class in PHP itself named Mutex:
http://php.net/manual/de/class.mutex.php

Please try the support build as the class has been renamed there.