First of all, I'm not the one developing this but I'm the one with the SO account. My SF knowledge is almost non-existent.
Basically, the problem is that a query is returning only 500 rows from our PHP script. However, when we substitute that query (directly within the PHP) with another, that query returns over 1500 rows. There are definitely over 500 rows that ought to be returned by the first query - I've checked using the data explorer.
Here's the first query:
And here is the second:
ORDER BY CreatedDate ASC
Any clues? I appreciate this might not be enough information but I don't know much about Salesforce. If there's anything else you'd need to answer this, ask and I'll see what I can do.