$physical_memory for Proxmox VE (VM OpenVZ)

Hello,

the variable: $ physical_memory returns 0 
when the script is used in a VM (Virtual Machine) in Proxmox VE OpenVZ 

ERROR :
Uncaught exception from user code:
	Illegal division by zero at ./mysqltuner.pl line 642.
 at ./mysqltuner.pl line 642
	main::calculations() called at ./mysqltuner.pl line 1010

FREE :
production@production:~# free -h
             total       used       free     shared    buffers     cached
Mem:            0B        22G        25G         0B         0B        21G
-/+ buffers/cache:       1.1G        46G
Swap:         2.0G         0B       2.0G

SYSTEM :
production@production:~# lsb_release -a
    No LSB modules are available.
    Distributor ID:	Debian
    Description:	Debian GNU/Linux 7.4 (wheezy)
    Release:	7.4
    Codename:	wheezy
production@production:~# cat /proc/version
    Linux version 2.6.32-19-pve (production@production) (gcc version 4.4.5 (Debian 4.4.5-8) )
production@production:~# getconf LONG_BIT
    32

thank you