Unexpected problem with "$vbulletin->" variable

[luroca]

Hello, this question is for vb 3.5.0 gold
If I used in /root/global.php:

eval('$candoit = in_array($vbulletin->userinfo[usergroupid], array(' . $vbulletin->options[can_do] . '));');

I get:
parse error, unexpected T_STRING in /home/myforum/public_html/vbtest/global.php on line xxx

When I used "in_array($bbuserinfo[usergroupid]" instead of "in_array($vbulletin->userinfo[usergroupid]" it was OK.

What´s wrong with "($vbulletin->userinfo[usergroupid]"?

Thanks in advance