1.11 is no longer supported please upgrade to 1.12.
Also you should really install the software yourself.
Since you used a 3rd party install we can't really support it as we do not know what they did to install it.
Looks like ini_set is disabled by your host.
The error says class PEAR is already declared. So either your host is doing something wonky and already declared it some how, or your source is not correct, or something is calling that file a second time that should not. Either way running 1.11 until 1.12 came out I never got this error so I would surmise that it is something specific to the way you installed, or your host.