Override example with Prestashop

gistfile1.php

<?php

class ObjectModel extends ObjectModelCore
{   
    public function add($autodate = true, $nullValues = false)
    {
        $result = parent::add($autodate, $nullValues);
        if ($result)  Module::hookExec('objectAdd', array('object' => $this));
        return $result;
    }

    public function update($autodate = true, $nullValues = false)
    {
        $result = parent::update($autodate, $nullValues);
        if ($result)  Module::hookExec('objectUpdate', array('object' => $this));
        return $result;
    }

    public function delete($autodate = true, $nullValues = false)
    {
        $result = parent::delete($autodate, $nullValues);
        if ($result)  Module::hookExec('objectDelete', array('object' => $this));
        return $result;
    }
}
?>