Avoid repository call in objects (ie lazy load)

location.php

<?php

namespace ezp\Content;

class Location extends Base implements \ezp\DomainObjectInterface
{
    // lots of stuff before

    /**
     * Parent Location of the Location or a Proxy object representing it
     *
     * @var Proxy|Location
     */
    protected $parent;
    // replace $parentId public property ?
    // and if we need to get only the parentId, we can add a dynamicProperty


    /**
     * Sets the parent
     *
     * @param Proxy|Location $parentLocation
     * @return void
     */
    protected function setParent( $parentLocation )
    {
        $this->parent = $parentLocation;
    }

    protected function getParent()
    {
        if ( $this->parent instanceof Proxy )
        {
            $this->parent = $this->parent->load();
        }
        return $this->parent;
    }

    // lots of stuff after
}

proxy.php

<?php

namespace ezp\Base;

class Proxy
{

    /**
     * A service object
     *
     * @var Service
     */
    protected $service;

    /**
     * ID of the object
     *
     * @var mixed
     */
    protected $id;

    /**
     * Method to use on the service to load the object
     * 
     * @var string
     */
    protected $method;

    /**
     * __construct
     *
     * @param Services $service
     * @param mixed $id
     * @param string $method
     */
    public function __construct( Services $service, $id, $method = 'load' )
    {
        $this->service = $service;
        $this->id = $id;
        $this->method = $method;
    }


    public function load()
    {
        return call_user_func( array( $this->service, $this->method ), $this->id );
    }

}

?>

As discussed it is a proxy object, and like collections it is generic, something like this perhaps:

interface Proxy
{
    public function __construct( Handler $handler, int $id, string $function = 'load' );

    /**
     * Load the object this proxy object represent
     *
     * @return DomainObject
     */
    public function load();
}