<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
   <SOAP-ENV:Body>
      <locationCollection>
         <Location>
            <name>AME s438</name>
            <id>452</id>
            <latitude>32.236322</latitude>
            <longitude>-110.951614</longitude>
         </Location>
         <Location>
            <name>ECE 229</name>
            <id>45</id>
            <latitude>32.235069</latitude>
            <longitude>-110.953417</longitude>
         </Location>
      </locationCollection>
   </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

However what I was getting instead was:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
   <SOAP-ENV:Body>
      <locationCollection>
         <SOAP-ENC:Struct>
            <name>AME s438</name>
            <id>452</id>
            <latitude>32.236322</latitude>
            <longitude>-110.951614</longitude>
         </SOAP-ENC:Struct>
         <SOAP-ENC:Struct>
            <name>ECE 229</name>
            <id>45</id>
            <latitude>32.235069</latitude>
            <longitude>-110.953417</longitude>
         </SOAP-ENC:Struct>
      </locationCollection>
   </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Here was my original code for the server:

<?php
$wsdl = 'http://example.com/locations_service.wsdl';
$service = new SoapServer($wsdl);

$service->addFunction('getComputerLabs');
$service->handle();

function getComputerLabs($input) {
  $all_locations = resource::get_all(FALSE, 'location');

  $return_array = array();

  foreach ($all_locations as $l) {

    // Build a basic return object.
    $new_loc = new Location();
    $new_loc->name = $l->name;
    $new_loc->id = $l->resource_id;
    $new_loc->latitude = $l->getProperty('Latitude');
    $new_loc->longitude = $l->getProperty('Longitude');

    $return_array[] = $new_loc;
  }

  return $return_array;
}

class Location {
    public $name;
    public $id;
    public $description;
    public $url;
    public $buildingName;
    public $roomNumber;
    public $openStatus;
    public $latitude;
    public $longitude;
}
?>

Apparently the SOAP library really prefers that everything is an object. In php 5 they added an ArrayObject class. This coupled with a SoapVar call fixed my output for me.

<?php
function getComputerLabs($input) {
  $all_locations = resource::get_all(FALSE, 'location');

  /**
   * Use an ArrayObject instead of a plain array.
   */
  $return_array = new ArrayObject();

  foreach ($all_locations as $l) {

    // Build a basic return object.
    $new_loc = new Location();
    $new_loc->name = $l->name;
    $new_loc->id = $l->resource_id;
    $new_loc->latitude = $l->getProperty('Latitude');
    $new_loc->longitude = $l->getProperty('Longitude');

    /**
     * Encode each array element with SoapVar.  Parameter 5 is the name of the
     * XML element you want to use.  This only seems to work within
     * an ArrayObject.
     */
    $new_loc = new SoapVar($new_loc, SOAP_ENC_OBJECT, null, null, 'Location');

    $return_array->append($new_loc);
  }

  return $return_array;
}
?>

Note that with only the ArrayObject part, and before I figured out the SoapVar wrapper, I was getting this interesting BOGUS tag:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
   <SOAP-ENV:Body>
      <locationCollection>
         <BOGUS>
            <name>AME s438</name>
            <id>452</id>
            <latitude>32.236322</latitude>
            <longitude>-110.951614</longitude>
         </BOGUS>
         <BOGUS>
            <name>ECE 229</name>
            <id>45</id>
            <latitude>32.235069</latitude>
            <longitude>-110.953417</longitude>
         </BOGUS>
      </locationCollection>
   </SOAP-ENV:Body>
</SOAP-ENV:Envelope>