<?php

class User extends Member {
    private static $db = array(
        "FirstName" => "Text",
        "Age" => "Int",
        "Address" => "Text"
    );

    public static $has_one = array(
        'Profile' => 'Profile'
    );


    public function onBeforeWrite()
    {
        parent::onBeforeWrite();
        if ($this->Profile()->exists()) {
            $profile = new Profile();
            $profile->User = $this;
            $profile->write();
        }
    }






<?php

class Profile extends DataObject {

    public static $has_one = array(
        'User' => 'User'
    );

    function getCMSFields() {
        $fields = new FieldList(new TabSet('Root'));
        return $fields;
    }

}






 public function addNew() {

        $NewUser = new User();
        $NewUser -> FirstName = "User First Name";
        $NewUser->write();

    }