modx 2.2 changes

$modx->getUser("contextname")
return anonymous user if no user is logged in to the context.
when getOne("Profile") is performed on anonymous user, will return null, so some error might be thrown.

modx->db->dbfunctions is now deprecated, so use the actual function from $modx itself.
for more information, refer here:
http://rtfm.modx.com/display/revolution20/Upgrading+MODx#UpgradingMODx-VersionSpecificChanges
http://rtfm.modx.com/display/revolution20/Summary+of+Legacy+Code+Removed+in+2.1

Example of a big change:

$modx->db->query is completely different from $modx->query

So you may use parseBinding to do your query.

Example:

$sSelectSQL = "select `parent`, `context_key` , id, `alias`, pagetitle, longtitle from modx_site_content where context_key=:contextand parent=:parent and `alias`=:alias and (published=0 or deleted=1)";

$aParam = array(":context" => "web",

":parent" => 1, ":alias" => "somealias");

$sResultSelectSQL = $modx->parseBindings($sSelectSQL, $aParam);

$stmt = $modx->query($sResultSelectSQL);

if (! $stmt) throw new Exception("SQL Failed: " . $sResultSQL);

//to fetch all

$aCount = $stmt->fetchAll(PDO::FETCH_ASSOC);

foreach($aCount as $oRow) {

  echo $oRow["id"];

}

//to fetch one

$oRow = $stmt->fetch($PDO::FETCH_ASSOC);

echo $oRow["id"];

And other class based method:

//to get an object row

$oRes = $modx->getObject("modResource", array("context_key" => "web", "parent" => 1, "alias" => "somealias"));

echo $oRes->get("id");