How to save custom value in DB from custom .module I have inherited a custom module, which groups together some field of an custom ContentType and sends it by email.

In the module there are 3 functions.

Email check preg match:

function __autoload($class_name) {
  require_once($class_name . '.lib.php');
}
require_once('vumclass.lib.php');


This function gets triggered when the node is saved or updated. Right?

function vumveranstaltungsmailer_action_info() {
  return array(
    'vumveranstaltungsmailer_action' =&gt; array(
      'type' =&gt; 'node',
      'label' =&gt; 'vumveranstaltungsmailer_action',
      'configurable' =&gt; FALSE,
      'triggers' =&gt; array('node_insert', 'node_update'),
    ),
  );
}


Do stuff, send email:

function vumveranstaltungsmailer_action($object, $context) {
//do Stuff, sends email. Not shown here.

//I want to set this field to empty/clear it
$object-&gt;field_email_mailer_01['und']['0']['value']-&gt;set(NULL);

}


Bare with me, I am pretty a beginner/noob. I am a bit overwhelmed where and how to do it. Please give me a simple solution, so I understand it. Quick and dirty is fine for me ;-)
Once you get your nid of the node you can use the code below to change the field value 

  $node = node_load($nid);

   unset($node-&gt;field_example['und'][0]['value']);
    //similarly for other fields you can change the value
    node_save($node);