Situation: I have few entities (task, client, ...) most of them needs same functionality like search by id, create, save, delete. Firstly I created services for each of them, and all services looked same (with same methods). So know I tried to use parent service to optimize code duplication. Is this the right way to use parent services?

BaseService.php

<?php
...

public function __construct(EntityManager $em, Paginator $paginator, EventDispatcherInterface $eventDispatcher, Router $router, $itemsPerPage)
{
    $this->em = $em;
    $this->paginator = $paginator;
    $this->eventDispatcher = $eventDispatcher;
    $this->router = $router;
    $this->itemsPerPage = $itemsPerPage;
}

public function setClass($class)
{
    $this->class = $class;
}

public function setRepo($repo)
{
    $this->repo = $repo;
}

public function get($id)
{
    return $this->repo->find($id);
}

// Other methods
...

ClientService.php

<?php

...

public function __construct(EntityManager $em, Paginator $paginator, EventDispatcherInterface $eventDispatcher, Router $router, $itemsPerPage, EntityRepository $repo)
{
    parent::__construct($em, $paginator, $eventDispatcher, $router, $itemsPerPage);
    $this->setClass('Client');
    $this->setRepo($repo);
}

services.xml

<service id="abstract_base_service" abstract="true">
  <argument type="service" id="doctrine.orm.entity_manager" />
  <argument type="service" id="knp_paginator"></argument>
  <argument type="service" id="event_dispatcher"></argument>
  <argument type="service" id="router"></argument>
  <argument type="string">%paginator.items_per_page%</argument>
</service>

<service id="base_service" class="%base_service.class%" parent="abstract_base_service" />

<service id="task_service" class="%task_service.class%" parent="base_service">
  <argument type="service" id="task.repository"></argument>
</service>

<service id="client_service" class="%client_service.class%" parent="base_service">
  <argument type="service" id="client.repository"></argument>
</service>

...

TaskService.php

<?php

...

public function __construct(EntityManager $em, Paginator $paginator, EventDispatcherInterface $eventDispatcher, Router $router, $itemsPerPage, EntityRepository $repo)
{
    parent::__construct($em, $paginator, $eventDispatcher, $router, $itemsPerPage);
    $this->setClass('Task');
    $this->setRepo($repo);
}

The base_service service does not have any value here, the others makes sense.

Yeah, my parent in task/client services must be abstract. Thanks!

I'd use a DIC extension to build these services based on a skeleton. See how doctrine does it. Inheritance is always the worst choice over composition