Adiciona atributo a um grupo do magento 1 / add custom attribute to a custom attribute_set's group

AddAttributeToGroupMagento.php

<?php
try {
    /* @var $installer Mage_Catalog_Model_Resource_Setup */
    $installer = new Mage_Catalog_Model_Resource_Setup('core_setup');
    $installer->startSetup();

    $attribute = 'attribute_code';
    $groupName = 'General'; // Or other 

    $entityTypeId = $installer->getEntityTypeId('catalog_product');
    $attributeSetId = $installer->getAttributeSet($entityTypeId, 'Default', 'attribute_set_id'); // Can be other if yout have custom attribute_set
    $attributeGroupId = $installer->getAttributeGroupId($entityTypeId, $attributeSetId, $groupName);

    // Add existing attribute to group
    $attributeId = $installer->getAttributeId($entityTypeId, $attribute);
    $installer->addAttributeToGroup($entityTypeId, $attributeSetId, $attributeGroupId, $attributeId, 35);

    $installer->endSetup();
} catch (Exception $e) {
    Mage::logException($e);
}