magento_soap_v2_catalog_product_create_attribute_options.php

<?php
$options = $proxy->catalogProductAttributeOptions($sessionId, '23');
foreach ($options as $opt) {
	if ($opt['label'] == 'yellow') {
		$color = $opt['value'];
	}
}
if (!isset($color)) {
	$color = $proxy->catalogProductAttributeAddOption('23','yellow');
}

$options = $proxy->catalogProductAttributeOptions('24');
foreach ($options as $opt) {
	if ($opt['label'] == 'XL') {
		$size = $opt['value'];
	}
}
if (!isset($size)) {
	$size = $proxy->catalogProductAttributeAddOption('24','XL');
}