Magento 1 - How to add attribute to the attribute set

lukas.php

<?php
require_once 'app/Mage.php';
Mage::app();


$attributeSetName = 'Electric scooters'; // Name of the attribute set
//$groupName = 'Frontend';
$code = 'my_attribute_code';

try {
    $setup = new Mage_Eav_Model_Entity_Setup('core_setup');

    $attributeSetId = $setup->getAttributeSetId('catalog_product', $attributeSetName);
    $attributeGroupId = $setup->getAttributeGroupId('catalog_product', $attributeSetId, null);
    $attributeId = $setup->getAttributeId('catalog_product', $code);

    $setup->addAttributeToSet($entityTypeId = 'catalog_product', $attributeSetId, $attributeGroupId, $attributeId);

   echo 'Added Attribute to SET ' . $attributeSetName . ' (' . $code . ')';
} catch (Exception $e) {
    echo 'ERROR when added Attribute to SET ' . $attributeSetName . ' (' . $code . ')';
}