product custom attribute multiselect not able to save the values

Question

I have created product custom attribute called package which is multiselect.

$this->addAttribute(
 'catalog_product',
 'packages',
 array(
 'group' => 'Package',
 'backend' => '',
 'frontend' => '',
 'class' => '',
 'default' => '',
 'label' => 'Packages',
 'input' => 'multiselect',
 'type' => 'text',
 'source' => 'npm_recurrex/package_source',
 'global' => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL,
 'is_visible' => 1,
 'required' => 0,
 'searchable' => 0,
 'filterable' => 0,
 'unique' => 0,
 'comparable' => 0,
 'visible_on_front' => 1,
 'user_defined' => 1,
 )
);

And the options for this fields get from the custom module called package where I create/edit the package entity.

enter image description here

Everything is fine, but only problem is When I am saving a product with custom attribute I am selecting multiple options, I mean I am selection package1 and package2 and save the product. Product saved successfully, but this is not saving my custom attribute selected values, custom attribute [multi select] not storing in database.

Can anybody suggest what is the wrong with this, Where I am not good in this process?

Thank you for valuable answers

Answer 1

You have to make sure, that magento changes your values to something which can be written to the database, an array can't.

so you need to add a backend model:

'backend' => 'eav/entity_attribute_backend_array',

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