Your request is a bit vague but it sounds like you want to dispense with the standard PHPBB forum/topic listing pages and instead let users search for a forum by entering it's name.
The form sounds pretty simple. Just a text input (let's assume its name is 'forumName') and a 'go' button. The logic to handle that submission would be pretty simple:
// PHP to handle your form submission
define('IN_PHPBB', true);
$phpbb_root_path = (defined('PHPBB_ROOT_PATH')) ? PHPBB_ROOT_PATH : './';
$phpEx = substr(strrchr(__FILE__, '.'), 1);
include($phpbb_root_path . 'common.'.$phpEx);
include($phpbb_root_path . 'includes/functions_display.' . $phpEx);
/* IMPORTANT - you should validate the forum name to prevent sql injection or something */
$sql = "SELECT * FROM phpbb_forums WHERE forum_name='" . $db->sql_escape($_POST['forumName']) . "'";
$result = $db->sql_query($sql);
$forums_found = array();
while($row = $db->sql_fetchrow($result)) {
$forums_found[] = $row
}
$db->sql_freeresult($result);
if (sizeof($forums_found) < 1) {
die('no rows found');
} else {
// display rows
}
You might have better luck posing this question on the phpbb forums.
