Magento visibility being reset

gistfile1.php

<?php
// If you have hidden products never do collection
// saving, without adding visibility attribute to select

$products = Mage::getModel('catalog/product')
                ->getCollection()
                // Important or visibility will be reset to default value (Visible in Catalog and Search)
                ->addAttributeToSelect(array('visibility', 'name'));

foreach ($products as $product) {
    $product->setSomething('someValue');
}

$products->save();