[Snippet] WebGroupJoin

//
// WebGroupJoin v0.1 for MODx
// (Tested on MODx 0.9.1)
//
// By Luca Allulli, February 2006
// License: GNU GPL
//

//Begin configuration

	//Web groups that web users are allowed to join/leave
		$webUserGroups=array("Teachers", "Students");
		
	//Message strings
		$submitButton="Subscribe";
		$successful="Successfully subscribed.";
		
//End configuration

$output="";
$uid=$modx->getLoginUserID();

if(!isset($uid)) return "";

$sql = 'SELECT webgroup FROM'.$modx->getFullTableName("web_groups").' WHERE webuser='.$uid.';';

$joinedGroups=$modx->db->getColumn("webgroup", $sql);


$sql = "SELECT id, name FROM".$modx->getFullTableName("webgroup_names")." WHERE name IN ('".implode("','",$webUserGroups)."');";

$rs=$modx->db->query($sql);

while($row=$modx->fetchRow($rs)) {
	$id=$row['id'];
	$webGroupName[$id]=$row['name'];
	$webGroupJoined[$id]=in_array($id, $joinedGroups);
}
	
if(!isset($webGroupName)) return "";
	
if(!isset($_POST['posted'])) {
	//Ask user for input
	
	$output.='<form action="index.php?id='.$modx->documentIdentifier.'" method="post">';
	$output.='<input type="hidden" name="posted" value="yes" />';
	foreach($webGroupName as $id => $name) {
		$output.='<input type="checkbox" name="group'.$id.'" ';
		if($webGroupJoined[$id])
			$output.='checked="checked" ';
		$output.='" />'.$webGroupName[$id].'<br />';		
	}
	$output.='<input type="submit" value="'.$submitButton.'" /></form>'."\n";

} else {
	//Process input
	
	foreach($webGroupJoined as $id => $joined) {
		if(isset($_POST['group'.$id]) && !$joined) {
			$sql = 'INSERT INTO '.$modx->getFullTableName("web_groups").' (id, webgroup, webuser) VALUES (NULL, '.$id.', '.$uid.');';
			
			$rs=$modx->db->query($sql);
			
		}
		if(!isset($_POST['group'.$id]) && $joined) {
			$sql = 'DELETE FROM '.$modx->getFullTableName("web_groups").' WHERE webgroup='.$id.' AND webuser='.$uid.';';
			
			$rs=$modx->db->query($sql);
		}
	}
	$output.=$successful;
}


return $output;