changeState API endpoint - sending multiple Ids

I have now resolved this issue using the bulk/execute endpoint as follows with the following request in case anybody else stumbles across the same issue as it took me a few hours to figure this out...

foreach($data as $ts) {
    $id = $ts['external_id'] //The External Reference from Clarizen TS
    $params['requests'][] = [
        'url' => "/data/changeState",
        'method' => 'POST',
        'body' => [
            'Ids' => ["/Timesheet/{$id}"],
            'state' => '{YOUR_REQUIRED_STATE}'
        ],
    ];
}
$this->clarizen = $this->curl_request('/bulk/execute', $params, 'post', $session, $server_details['serverLocation']);
$this->clarizen = json_decode($this->clarizen, true);

foreach($this->clarizen['responses'] as $message) {
    if($message['statusCode'] != 200) {
        $errors[] = $message['body']['message'];
    }
}

if(!empty($errors)) {
    var_dump($errors); //There will be multiple requests with potentially different errors, log them all.
    exit(1);
}