Symfony 3 form multiple file upload issue

I've been trying to upload multiple files in a form but I just cannot find a solution that would work for me. Whenever I add multiple files to my input, only one of those files gets passed to the controller and uploaded.

Controller.php

        // File uploading
        $files = $auto->getImages();
        $images = array();

        if($files != null) {
            $key = 0;

            foreach ($files as $file)
            {
                $fileName = md5(uniqid()) . '.' . $file->guessExtension();
                $file->move(
                    $this->getParameter('car_adds'),
                    $fileName
                );
                $images[$key++] = $fileName;
            }
            $auto->setImages($images);
        }

$auto->getImages() gives me a string value instead of an array value, therefor, whenever I try to foreach loop it I get an empty result and no file upload.

I tried renaming my image form widget to "form[images][]" instead of "form[images]" which is generated by the formbuilder however when I do that I get the following error:

FormType.php

          ->add('images', FileType::class, array(
            'label' => false,
            'data_class' => null,
            'label_attr' => array('class' => $label_offset),
            'required' => false,
            'attr' => array(
                'class' => $styles,
                'multiple' => true)))

Entity.php

    /**
* @var array
*
* @Assert\Image(
*     mimeTypes = {
*   "image/png",
*   "image/pjpeg",
*   "image/jpeg",
*   "image/gif"
* },
*     mimeTypesMessage="Failas yra netinkamo formato",
*     maxSize = "10M",
*     maxSizeMessage="Failas yra per didelis"
* )
* @ORM\Column(name="images", type="array", nullable=true)
*/
private $images;

 /**
 * Set images
 *
 * @param array $images
 *
 * @return Auto
 */
public function setImages($images)
{
    $this->images = $images;

    return $this;
}

/**
 * Get images
 *
 * @return array
 */
public function getImages()
{
    return $this->images;
}

This is my first project that I'm trying to build with Symfony 3 so I'm assuming there must be something that I may have overlooked.