doctrine2/manual/docs/Object relational mapping - Relations - Inheritance - One table one class.php

In the following example we have three database tables called 'entity', 'user' and 'group'.
Users and groups are both entities.
The only thing we have to do is write 3 classes (Entity, Group and User) and make iterative
setTableDefinition method calls.
<br /><br />

<code type="php">
class Entity extends Doctrine_Record { 
    public function setTableDefinition() {
        $this->hasColumn('name','string',30);
        $this->hasColumn('username','string',20);
        $this->hasColumn('password','string',16);
        $this->hasColumn('created','integer',11);
    }
}

class User extends Entity { 
    public function setTableDefinition() {
        // the following method call is needed in
        // one-table-one-class inheritance
        parent::setTableDefinition();
    }
}

class Group extends Entity {
    public function setTableDefinition() {
        // the following method call is needed in
        // one-table-one-class inheritance
        parent::setTableDefinition();
    }
}
</code>