I don's see a way to fix this. PHP is not able to keep several elemtns with the same names in object or array. So it is not possible to keep order of elements with different names.

You can probaly change WSDL to have a sequence of 'words', where each word is an element defined as extension of type 'string' with 'part_of_speach' attribute. So you'll have to pass something like this:

<sentence>
  <word part_of_speach="other">The</word>
  <word part_of_speach="noun">cat</word>
  <word part_of_speach="other">is</word>
  <word part_of_speach="verb">playing</word>
  <word part_of_speach="other">with</word>
  <word part_of_speach="noun">string</word>
</sentence>

In practice, that's not possible. The 'words' example is a much-simplified example of what I want to happen. In reality my document is a sequence of objects of different types, but must remain in the correct order.

Think of an XHTML document. It's valid XML and could theoretically be used in a similar way. However, in such a document you've got no idea whether a <p> element, a <ul> element, a <div>, a <form>, or a <table> is coming next... But they do have to have the order retained. If you globbed all of the paragraps together, with all of the unordered lists after, you'd end up with something that didn't make much sense.

In fact, if you look at the schema for XHTML (http://www.w3.org/TR/xhtml1-schema/#xhtml1-strict) you can see that it uses exactly this mechanism (xs:choice maxOccurs="unbounded") in order to implement this. (See the "Block" complexType) -- So, if you want to parse soap messages with an XHTML payload correctly, a solution to this problem needs to be found.

You can access element order using the following trick.

<?php
$wsdl = "http://zx81.highlyillogical.org/~simon/phpbugtest/phpbugtest.wsdl";
$options=Array(
		'typemap' => array(array("type_ns"   => "http://zx81.highlyillogical.org/~simon/phpbugtest",
		                         "type_name" => "sentence",
		                         "from_xml"  => "sentence_from_xml"))
		);

function sentence_from_xml($x) {
	return simplexml_load_string($x);
}

$client = new SoapClient($wsdl, $options) ;
$result = $client->bugtest(); 
var_dump($result);
foreach ($result as $key => $val) {
	echo $key . ":" . (string)$val . "\n";
}

Actual result:
--------------
object(SimpleXMLElement)#2 (3) {
  ["other"]=>
  array(3) {
    [0]=>
    string(3) "The"
    [1]=>
    string(2) "is"
    [2]=>
    string(4) "with"
  }
  ["noun"]=>
  array(2) {
    [0]=>
    string(3) "cat"
    [1]=>
    string(6) "string"
  }
  ["verb"]=>
  string(7) "playing"
}
other:The
noun:cat
other:is
verb:playing
other:with
noun:string

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

Yeah, I'm happy to write my own serialisers and deserialisers, to work around the problem. (Although it's time consuming -- I don't have to do this in other languages) 

That 'typemap' trick doesn't seem to be documented anywhere or I'd have gone with it straight away.

I haven't made it work in practice yet, but it looks like it should work. I can implement my own complex classes and ensure that I (de)serialize everything in the correct order.

There is no way to automatic preserve order of objects without breaking compatibility, however as I showed, it is possible to do this with sereral lines of additional code.

So nothing to fix (except documentation).

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.

"The typemap option is an array of type mappings. Type mapping is an array with keys type_name, type_ns (namespace URI), from_xml  (callback accepting one string parameter) and to_xml  (callback accepting one object parameter)."