php-ews and email IDs

Question

I'm working on a php script that connects to an exchange server using php-ews. For starters I pulled all emails in my inbox and did some digging to see how chain emails work. I want to be able to group email chains together for simplicity reasons. What I found is 2 emails completely unrelated my have the same exact ID. ChangeKeys appear to be unique, but chain emails have unique changekeys therefore I can't group them together based on that. Any ideas on how I can get a "chain email" unique ID?

Below is the script "out of the box":

<?php
set_time_limit(120); 
require_once('autoload.php');
require_once('credentials.php');

//$ews = new ExchangeWebServices("hostname", "username", "password", ExchangeWebServices::VERSION_2010);
$ews = new ExchangeWebServices($host, $username, $password);

$request = new EWSType_FindItemType();
$request->ItemShape = new EWSType_ItemResponseShapeType();
$request->ItemShape->BaseShape = EWSType_DefaultShapeNamesType::DEFAULT_PROPERTIES;

$request->Traversal = EWSType_ItemQueryTraversalType::SHALLOW;

// Limits the number of items retrieved
$request->IndexedPageItemView = new EWSType_IndexedPageViewType();
$request->IndexedPageItemView->BasePoint = "Beginning";
$request->IndexedPageItemView->Offset = 0; // Item number you want to start at
$request->IndexedPageItemView->MaxEntriesReturned = 1000; // Numer of items to return in total

$request->ParentFolderIds = new EWSType_NonEmptyArrayOfBaseFolderIdsType();
$request->ParentFolderIds->DistinguishedFolderId = new EWSType_DistinguishedFolderIdType();
$request->ParentFolderIds->DistinguishedFolderId->Id = EWSType_DistinguishedFolderIdNameType::INBOX;

// sort order
$request->SortOrder = new EWSType_NonEmptyArrayOfFieldOrdersType();
$request->SortOrder->FieldOrder = array();
$order = new EWSType_FieldOrderType();

// sorts mails so that oldest appear first
// more field uri definitions can be found from types.xsd (look for UnindexedFieldURIType)
$order->FieldURI = '';
@$order->FieldURI->FieldURI = 'item:DateTimeReceived'; // @ symbol stops the creating default object from empty value error
$order->Order = 'Ascending'; 
$request->SortOrder->FieldOrder[] = $order;

$response = $ews->FindItem($request);

//For Debugging
//die("<pre>" . print_r($response, 1) . "</pre>");

if(!isset($response->ResponseMessages->FindItemResponseMessage->RootFolder))
{
    $responseMessage = $response->ResponseMessages->FindItemResponseMessage;
    die("<h3 style='text-align: center;'>Email</h3>" . $responseMessage->MessageText . "<br /><br />" . $responseMessage->ResponseCode);
}
else
    $totalItems = $response->ResponseMessages->FindItemResponseMessage->RootFolder->TotalItemsInView;

$emails = array();

$rootFolder = $response->ResponseMessages->FindItemResponseMessage->RootFolder;
$messages = $rootFolder->Items->Message;
$lastItemInRange = $rootFolder->IncludesLastItemInRange;
$i = 1; // Counter to multply the max etries retrurned, to create the offset value

while($lastItemInRange != 1) // While the last item in the inbox is strill not in range retrieve the next 1000 messages
{
    $limit = $request->IndexedPageItemView->MaxEntriesReturned;
    $request->IndexedPageItemView->Offset = $limit * $i;

    $response = $ews->FindItem($request);

    $rootFolder = $response->ResponseMessages->FindItemResponseMessage->RootFolder;
    $messages = array_merge($messages, $rootFolder->Items->Message);
    $lastItemInRange = $rootFolder->IncludesLastItemInRange;
    echo '<pre>';
    print_r( $messages);
    echo '</pre>';
    $i++;
}

?>

And below is an email example returned:

[100] => stdClass Object
        (
            [ItemId] => stdClass Object
                (
                    [Id] => XXXXXXXXXXXXXXXXX
                    [ChangeKey] => XXXXXXXXXXXXXXXXXXXX
                )

            [Subject] => Test Email
            [Sensitivity] => Normal
            [Size] => 30200
            [DateTimeSent] => 2016-02-01T21:43:06Z
            [DateTimeCreated] => 2016-02-01T21:43:09Z
            [HasAttachments] => 
            [From] => stdClass Object
                (
                    [Mailbox] => stdClass Object
                        (
                            [Name] => Test User
                            [EmailAddress] => [email protected]
                            [RoutingType] => SMTP
                        )

                )

            [IsRead] => 1
        )

Answer 1

The reason you're not getting more data from your mailItem has to do with your request->ItemShape->BaseShape. You've got it set to default properties, which doesn't include what you want, which is conversationId. Setting it to AllProperties will return a conversationId as part of your MessageItem, which will be an ItemIdType, so it'll have an id and a changeKey.

As a side note, I'd recommend not using that version of php-ews. It's out of date, unmaintained and doesn't follow any of the PSR's. I maintain my own fork, garethp/php-ews. You should find it easier to work with as a whole

Edit: A quick bit of information. The changeKey is only something you'll want to use to keep track of the state of an object. If an object is changed, it's changeKey will also change. It's mostly useful for knowing if the data you have is out of date or not.