PHP XML API不返回所有数据

Question

I am working on a project where I must pull data from an XML API using PHP cURL.

I am unable to retrieve very large data sets from the API, for example I have no issue pulling 500 user email addresses. But if I am pulling a list of 15,000 email addresses I only get about 4,000 back and the request takes about 3 minutes.

I have adjusted the timeout in php.ini which did not help.

My thought is to retrieve the data in batches and then append to the data pulled in. I am pretty new to PHP/back end scripting so forgive me if this seems like a simple question.

My research has shown array_chunk may be useful, but wouldn't that need the full amount of data to chunk anyway? Or could I pull the data in as a chunk, go back to where I left off in the data set and rinse/repeat?

Here is the code I have so far.

  function load_users($username, $token, $path, $list_id)
{
    $xml = '<xmlrequest>
    <username>'.$username.'</username>
    <usertoken>'.$token.'</usertoken>
    <requesttype>subscribers</requesttype>
    <requestmethod>GetSubscribers</requestmethod>
    <details>
    <searchinfo>
    <List>
    '.list_id.'
    </List>
    <Email></Email>
    </searchinfo>
    </details>
    </xmlrequest>';

    $ch = curl_init($path);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, $xml);
    $result = @curl_exec($ch);
    curl_close($ch);
    $xml_doc = simplexml_load_string($result);
    return $xml_doc;
}