How to add a custom or third JS file via layout block for Magento

You can use “action” element with “method” attribute from your Magento template XML file or backend – Page Layout (CMS) / Custom Design (Category)/ Custom Layout Update (Product) to append a custom or third JS file for your Magento

<reference name="blockname">
    <action method="addItem">
        <type>skin_js</type>
        <name>js/file.js</name>
        <params />
    </action>
</reference>

How can I get referrer URL in Magento, which Magento core function should I call

You can use getServer() method to retrieve HTTP_REFERER info

Mage::app()->getRequest()->getServer('HTTP_REFERER');

I would like to create a new Magento admin account, How can I do it programmatically

You need to use ‘admin/user’ model to create a new admin account and assign Magento role to new Magento admin account

$user = Mage::getModel('admin/user')->setData(array(
    'username'  => 'adminusername',
    'firstname' => 'admin first name',
    'lastname'  => 'admin last name',
    'email'     => 'admin@example.com',
    'password'  => 'password',
    'is_active' => 1
))->save();

$user->setRoleIds(array(1)) //Administrator role id is 1
->setRoleUserId($user->getUserId())
->saveRelations();

What method should I call to get all Magento Store Ids programmatically

You can use method – getStores to get all Magento store objects

$allStores = Mage::app()->getStores();
foreach ($allStores as $k => $val){
    $storeId = Mage::app()->getStore($k)->getId();
}

I would like to get a Magento product list and filter by Magento attributes

You can use method “addAttributeToFilter” to filter the Magento product list based on the Magento attributes.

$products = Mage::getModel('catalog/product')
->getCollection()
->addAttributeToSelect('*')
->addAttributeToFilter('attribute_code','attribute_value');

How can I get Magento upsell products list if only have product id

Have to load Magento product object first and call “getUpSellProductCollection” method to retrieve Magento upsell products list

$product_id = 1;
$pobject = Mage::getModel('catalog/product');
$product = $pobject->load($product_id);
$upsell_product = $product->getUpSellProductCollection()->addAttributeToSort('position', Varien_Db_Select::SQL_ASC)->addStoreFilter();

How can I check whether a Magento product is saleable or not programatically

You can use method – isSaleable from Magento product object to check if the Magento product is saleable or not

if(!$_product->isSaleable()): 
echo "Out of stock";
endif; 

How can I set current Magento store by store id programmatically

You can use use setCurrentStore and then call Mage::run to set current Magento store by store id programmatically

$store_id = 'store id';
$mageRunCode = 'store view code';
$mageRunType = 'store';

Mage::app()->setCurrentStore($store_id);
Mage::run($mageRunCode, $mageRunType);

I tried to use getProductUrl to get Magento product url, but it returns SEO unfriendly url. How can I retrieve the SEO friendly URL of a Magento product

You can use method “getUrlPath” to get the SEO friendly URL of a Magento product

/** Load Magento product by ID **/

$_product = Mage::getModel('catalog/product')->load($productID);
$url = $_product->getUrlPath();