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.

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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