<?php
// Magento login information
$mage_url = 'http://YOUR_MAGENTO_SERVER/index.php/api/?wsdl';
$mage_user = 'YOUR_SOAP_USER';
$mage_api_key = 'YOUR_SOAP_PASS';

// Initialize the SOAP client
$soap = new SoapClient($mage_url);

// Login to Magento
$sessionId = $soap->login($mage_user, $mage_api_key);

// create new category
$categ = array(
    15334,
    array(
        'name' => 'New Category 1',
        'is_active' => 1,
        'available_sort_by' => array('name', 'price'),
        'default_sort_by' => 'name'
    ),
    '0'
);

try {
    $id = $soap->call($sessionId, 'category.create', $categ);
}
    catch(Exception $e) {
    print("Error: ".$e->getMessage()."n");
}
?>