[noppid]

PHP Code:

if( $bbuserinfo['userid'])
{
$record_count = $DB_site->query_first("SELECT count(*) as r_count FROM ". TABLE_PREFIX ."thread WHERE postuserid='$bbuserinfo[userid]' and forumid = 'xx'");

if( $record_count )
     $posted_intro = true;
} 


Something like that in php_include_start should do it, but be aware, running this for every logged in user will cost ya. You are hitting two indexes to get that result, however, thread can be a big table.

That is not tested.