Error when I use this variable!

[jer79]

Hello,
I have a question about $g_enable_email_notification variable.
When I put it in my confi_inc.php file, my pages keep white and on the error_log file I can see this message:
[client 10.68.150.80] PHP Parse error: parse error, unexpected T_VARIABLE in /var/www/html/mantis/config_inc.php on line 41, referer: http://my ip adress/mantis/my_view_page.php

Line 41 I have that:
$g_administrator_email = 'my email adress';

What is this T_VARIABLE

Thanks for your help!

My version is: mantis 1.0.0