Your server has disabled core PHP functions via the disable_functions directive in php.ini. Depending on the functions that have been disabled, this may cause unexpected problems in XenForo. All PHP functions should be enabled. These may affect the proper execution of XenForo at times and should be resolved if possible. I contacted my host about this warning message, and their response was asking what PHP functions I require to be enabled? Therefore, if someone could let me know what PHP functions xenforo will need, I can pass that information on to my host. Thank you.