magento_soap_v2_catalog_product_create_simple.php

<?php
$proxy->catalogProductCreate($sessionId, 'simple', '4', 'simple_sku_yellow_XL',
    array(
        'name'                  => 'Product name',
        'description'           => 'Description Text...',
        'short_description'     => 'Short Description Text...',
        'websites'              => array(1),
        'price'                 => 100.00,
        'visibility'            => 1,
        'additional_attributes' => array('single_data' => array(array(
            'key' => 'color',
            'value' => $color
        ),array(
            'key' => 'size',
            'value' => $size
        )))
    )
);