[horde] What is meant with 'value' => 'a:0:{}' ?

[Ralph Ballier]

Hello,

I try to understand the configuration of Horde. Sometimes there is a
detailed information in the files, but sometime I don't find anything.

An example is: 'value' => 'a:0:{}' I don't understand it. Where I can
refer about this? 

Thanks
Ralph