php.ini extreme security in disable_functions;

system, system_exec, passthru, shell, shell_exec, exec, popen, pclose,
proc_open, proc_nice, proc_terminate, proc_get_status, proc_close, pfsockopen,
leak, apache_child_terminate, posix_kill, posix_mkfifo, posix_setpgid,
posix_setsid, posix_setuid, escapeshellcmd, escapeshellarg, phpinfo