Symfony Doctrine : fetch a collection persisted as array

I think you need a ManyToOne relationShip ... as I know, we never store an array in database.

in your example order can have many modules and module can have just one order ... in this case order called owning side and module called invers side ... and module keep id of order ...

look at this example

Table: Orders

id | user_id | ... | created_at          |
----------------------------------------------------
1  | 12      | ... | 2018-07-28 00:00:00 |
----------------------------------------------------

Table: Modules

id | order_id | ... | created_at          |
----------------------------------------------------
1  | 1        | ... | 2018-07-28 00:00:00 |
----------------------------------------------------
2  | 1        | ... | 2018-07-29 00:00:00 |
----------------------------------------------------

you must write your code like this...

Order Class

class Order implements OrderInterface
{

     /**
     * @var Collection
     *
     * @ORM\OneToMany(targetEntity="Module", mappedBy="order", cascade={"persist"})
     */
    protected $modules;

     /**
     * Don't forget initial your collection property 
     * Order constructor.
     */
    public function __construct()
    {
        $this->modules = new ArrayCollection();
    }

        /**
     * @return Collection
     */
    public function getModules(): Collection
    {
        return $this->modules;
    }

    /**
     * @param ModuleInterface $module
     */
    public function addModule(ModuleInterface $module): void
    {
        if ($this->getModules()->contains($module)) {

            return;
        } else {

            $this->getModules()->add($module);
            $module->setOrder($this);
        }
    }

    /**
     * @param ModuleInterface $module
     */
    public function removeModule(ModuleInterface $module): void
    {
        if (!$this->getModules()->contains($module)) {

            return;
        } else {

            $this->getModules()->removeElement($module);
            $module->removeOrder($this);
        }
    }
}

Module Class

class Module implements ModuleInterface
{
    /**
     * @var OrderInterface
     *
     * @ORM\OneToMany(targetEntity="Order", mappedBy="modules", cascade={"persist"})
     */
    protected $order;

    /**
    * @param OrderInterface $order
    */
    public function setOrder(OrderInterface $order) 
    {

        $this->order = order;
    }

    public function getOrder(): OrderInterface
    {
        return $this->order;
    }
}

when you persist order object by doctrine... doctrine handle this and create items