[cinq]

Odd, previous solutions provided should work.

ie.

PHP Code:

$prevpost = $DB_site->query("SELECT threadid FROM post WHERE title LIKE '%$formtitle%' LIMIT 1");
if($result=$DB_site->fetch_array($prevpost))
{
 $output = $result['threadid'];
} 


With $formtitle being the variable you want to compare the post table with to find a post with similar title.

$output should return the result ( threadid ) if there is such a match.