PHP Fatal error: Call to undefined function chdir()
chdir() and max() are built in functions that always exists in PHP. They are in no plugin, just a core. Even in safe mode both should be defined. 

There is one way to disable them and make them non-existent from the script's point of view. disable_functions section in php.ini does the trick. Usually it is used for safety, like this:

disable_functions=exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source 


and whilst I can see some illusionary* safety in disabling chdir(), disabling max() must have been a mistake. Note that on some configurations you can alter ini settings in .htaccess and via ini_set() too.

*Illusionary due to the same reasons that made Safe Mode deprecated.