Fault Code	Fault Message
100	Requested store view not found.
101	Requested website not found.
102	Category not exists.
103	Invalid data given. Details in error message.
104	Category not moved. Details in error message.
105	Category not deleted. Details in error message.
106	Requested product is not assigned to category.

		function getSomeRandomCategory(&$categories, $targetLevel, $currentLevel = 0) {
    if (count($categories)==0) {
        return false;
    }
    if ($targetLevel == $currentLevel) {
        return $categories[array_rand($categories)];
    } else {
        return getSomeRandomCategory($categories[array_rand($categories)]['children'], $targetLevel + 1);
    }
}

$proxy = new SoapClient('http://magentohost/api/soap/?wsdl');
$sessionId = $proxy->login('apiUser', 'apiKey');
$allCategories = $proxy->call($sessionId, 'category.tree'); // Get all categories.

// select random category from tree
while (($selectedCategory = getSomeRandomCategory($allCategories, 3)) === false) {}

// create new category
$newCategoryId = $proxy->call(
    $sessionId,
    'category.create',
    array(
        $selectedCategory['category_id'],
         array(
                'name'=>'Newopenerp',
                'is_active'=>1,
                'include_in_menu'=>2,
                'available_sort_by'=>'position',
                'default_sort_by'=>'position'
               )
    )
);

$newData = array('is_active'=>1);
// update created category on German store view
$proxy->call($sessionId, 'category.update', array($newCategoryId, $newData, 'german'));

$firstLevel = $proxy->call($sessionId, 'category.level', array(null, 'german', $selectedCategory['category_id']));

var_dump($firstLevel);

// If you wish remove category, uncomment next line
//$proxy->call($sessionId, 'category.delete', $newCategoryId);
		

		$proxy = new SoapClient('http://magentohost/api/soap/?wsdl');
$sessionId = $proxy->login('apiUser', 'apiKey');

$categoryId = 5; // Put here your category id
$storeId = 1; // You can add store level

$assignedProducts = $proxy->call($sessionId, 'category.assignedProducts', array($categoryId, $storeId));
var_dump($assignedProducts); // Will output assigned products.

// Assign product
$proxy->call($sessionId, 'category.assignProduct', array($categoryId, 'someProductSku', 5));

// Update product assignment postion
$proxy->call($sessionId, 'category.updateProduct', array($categoryId, 'someProductSku', 25));

// Remove product assignment
$proxy->call($sessionId, 'category.removeProduct', array($categoryId, 'someProductSku'));
		

Module: Mage_Catalog

Category

Faults

Example 1. Working with categories

Example 2. Working with assigned products