Tca Hook

ext_localconf.php

$hookPath = "EXT:extName/Classes/TcaHooks/class.Tx_extName_tcemainprocdm.php:Tx_extName_tcemainprocdm";
$GLOBALS["TYPO3_CONF_VARS"]["SC_OPTIONS"]["t3lib/class.t3lib_tcemain.php"]["processDatamapClass"][] = $hookPath;

Tx_extName_tcemainprocdm

class Tx_extName_tcemainprocdm {
    function processDatamap_postProcessFieldArray($status, $table, $id, &$fieldArray) {
        if ($status == 'update' && $table == 'fe_users') {
        }
    }
}