catalogProductUpdate multiple category IDs - php

Question

I'm trying to update the website and category IDs for a number of products in Magento and I'm having issues. Here's my code:
$client = new SoapClient('http://magentohost/api/v2_soap/?wsdl');
$session = $client->login('apiUser', 'apiKey');
$productarray = array("12345" => "1,2,3", "67890" => "1,5,6");
foreach ($productarray as $product_id => $cats) {
$update = array(
'websites' => array(1,2,3),
'categories' => array($cats)
);
$updatewebsite = $client->catalogProductUpdate($session,$product_id,$update);
}
When I run this code, it's changing the products to have the new website IDs but it's only updating the category IDs with the first one in $cats.
For example, "12345" will only have category ID 1 and not 2 or 3 as it should have.
When I print out what $cats is for each product, it's showing me the info correctly (as "1,2,3" and "1,5,6" for the examples above).
I'm not sure what I've done but I just can't seem to get it to update all the category IDs. I've got thousands of products to run through that all have different category IDs so I can't be doing this manually!
EDIT - SOLVED
I've changed my code so it's now like this (which works):
$client = new SoapClient('http://magentohost/api/v2_soap/?wsdl');
$session = $client->login('apiUser', 'apiKey');
$productarray = array("12345" => "1,2,3", "67890" => "1,5,6");
foreach ($productarray as $product_id => $cats) {
$cats = explode(",", $cats);
$update = array(
'websites' => array(1,2,3),
'categories' => $cats
);
$updatewebsite = $client->catalogProductUpdate($session,$product_id,$update);
}

Answer 1

The categories property would expect an array of IDs, whereas you're passing a string. Try using explode() to break it up:
foreach ($productarray as $product_id => $cats) {
$update = array(
'websites' => array(1,2,3),
'categories' => explode(',', $cats)
);
$updatewebsite = $client->catalogProductUpdate($session,$product_id,$update);
}