PHP - problem with underscore

[neverstop]

Hi I am trying to modify some code to add an avatar. Here is the line of code:

PHP Code:

$spitblogs .= "<div style=\"float:left;padding:5px\"><img width=\"50px\" src=\"customavatars/avatar$userid_$blog_avatar.gif\" class=\"inlineimg\" /></div><a style=\"font-size:12px\" href=\"{$vbulletin->options[bburl]}/blog.php?b=$blogid\"><strong>$blog_title</strong></a><br /><span class=\"shade\">$blog_dateline by $blog_username</span><br />"; 


The problem is with customavatars/avatar$userid_$blog_avatar.gif

When ever I try it the underscore after $userid is wreaking havoc with me. When I add the underscore $userid no loger works. Im sure this is an easy fix but I am not a programmer.

Thanks in advance,
Ian