Here is an example that works out of the box (with our simulation server):

$EasyDAClient = new COM("OPCLabs.EasyDAClient.5.0"); $ItemIds = new VARIANT(array("Simulation.Random", "Trends.Ramp (1 min)", "Trends.Sine (1 min)", "Simulation.Register_I4")); $Results = $EasyDAClient->ReadMultipleItems("", "OPCLabs.KitServer", $ItemIds); foreach ($Results as $X) print $X->Vtq->ToString()."";
It produces following output (e.g.):

1.25125888851588E-03 {VARTYPE(5)} @7/28/2010 6:13:40 PM; OPCQUALITY(192)
0.667287677526474 {VARTYPE(5)} @7/28/2010 6:13:40 PM; OPCQUALITY(192)
-0.867969703914737 {VARTYPE(5)} @7/28/2010 6:13:40 PM; OPCQUALITY(192)
0 {VARTYPE(3)} @7/28/2010 6:13:40 PM; OPCQUALITY(192)

This is with QuickOPC-COM 5.01.274.1, and PHP 5.2.12. There may be no one-line way to convert the resulting VT_ARRAY back to normal PHP array, but accessing the elements, and the use of 'foreach', is possible, so you can always convert it to anything you like, in a loop. I have searched the Web a little and assembled a list of related links, just in case:
www.mail-archive.com/php-bugs@...
www.colorpilot.com/blog/com-ar...
bugs.php.net/bug.php?id=39596
www.phpwelt.net/handbuecher/cz...
www.nme.at/download/phpcon02_m...
osdir.com/ml/php-windows/2010-...
<a href="forums.devnetwork.net/viewtopic.php?f=14&t=3599" target="_blank" rel="nofollow">forums.devnetwork.net/viewtopi...
www.colorpilot.com/pdfcreatorp...

Technically speaking, the variant on input, for arrays, should be VT_ARRAY | VT_xxxx, where VT_xxxx is an element type - the type that is accepted by a ReadItem for the same argument, or anything that can be converetd to that type. So, for example, for an input array of OPC Item IDs, the type on input should be VT_ARRAY | VT_BSTR, or convertible to it.
On ReadMultipleItems output, the type is VT_ARRAY | VT_VARIANT. The individual elements then hold interface pointers to DAVtq objects.
Each tool or language then has its own way of expressing the arrays, composing them or accessing their elements, so the above information may not be of direct use. And yes, arrays do not "per se" convert to strings. We currently do not have a specific example of how to work with arrays in PHP, but I will try to create it for you; for start, please send me (post here) your current code, so that I can investiage what is happening in there.