M1 Import Values to Dropdown/Multiple Select Attributes

This code is for Magento 1, it won't work in Magento 2.

Sometime when you need to deal with import of lots of values for a multiple select/drop down attribute. Then manual data entry is not very convenient. The code below will allow you to put all your values into a single text file and import in seconds. First you will need to upload the source code below into a new file manufacturer_import.php in the Magento root directory.

The above code will import Manufacturers into the “manufacturer” attribute, but can be used on any drop-down or multiple select attribute configured in Magento, simply change “manufacturer” at the end of line 6 to the code of the attribute you wish to update.

Next step is to prepare and upload your list of manufactures in a simple text file, one value per line. Save the file as “import.txt”, and upload into Magento root directory, beside the above script.

Apple
Banana
Pear
...

Navigate to www.example.com/manufacturer_import.php and you sould see the import successful message.

Source: http://www.magentocommerce.com/wiki/