Mass Products Stock levels Update in Magento

Step 1:

Create a CSV with a minimum of 3 columns, the SKU, qty and is_in_stock.
Then save it to "/app/var/import/updateStockLevels.csv".
For instance, we will use,

"sku","qty","is_in_stock"
"prod1","100","1"

Step 2:

Copy the code below into a new file "updateStock.php" and place this file in your root folder

define('MAGENTO', realpath(dirname(__FILE__)));
 require_once MAGENTO . '/app/Mage.php';
 umask(0); $count = 0;
 Mage::app()->setCurrentStore(Mage_Core_Model_App::ADMIN_STORE_ID);
 
 $file = fopen(MAGENTO . '/var/import/updateStockLevels.csv', 'r');
 while (($line = fgetcsv($file)) !== FALSE) {
   if ($count == 0) {
   foreach ($line as $key=>$value) {
   $cols[$value] = $key;
   }
 }
 
 $count++;
 if ($count == 1) continue;
 
 #Convert the lines to cols
 if ($count > 0) {
   foreach($cols as $col=>$value) {
   unset(${$col});
   ${$col} = $line[$value];
   }
 }
 
 // Check if SKU exists
 $product = Mage::getModel('catalog/product')->loadByAttribute('sku',$sku);
 if ( $product ) {
   $productId = $product->getId();
   $stockItem = Mage::getModel('cataloginventory/stock_item')->loadByProduct($productId);
   $stockItemId = $stockItem->getId();
   $stock = array();
   if (!$stockItemId) {
     $stockItem->setData('product_id', $product->getId());
     $stockItem->setData('stock_id', 1);
     } else {
       $stock = $stockItem->getData();
   }
 
   foreach($cols as $col=>$value) {
   $stock[$col] = $line[$value];
   }
 
   foreach($stock as $field => $value) {
   $stockItem->setData($field, $value?$value:0);
   }
 
 $stockItem->save();
 unset($stockItem); unset($product);
 }
 echo "
Stock updated $sku"; 
}
 fclose($file);

Step 3:

Run the php script in  Your browser like "www.YourDomain.com/updateStock.php".
Thats it. You are done.