Description:
------------
On of our suppliers expects heavily nested XML in the request we make.

Constructions like the following are not uncommon in the requests we have to make to them:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Body>
    <element1>
        <element2>
          <element3>
              <element4>
                <foo>bar</foo>
              </element4>
          </element3>
        </element2>
    </element1>
</SOAP-ENV:Body>

In order to create these nested structures, we used a helper as mentioned in the test script.

In PHP 5.4.45 it produced the XML as stated above. However, under PHP 7.0.5, the following XML is generated:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Body>
    <element1/>
</SOAP-ENV:Body>

For other people affected by this bug, if you replace the buildElement function with the following code, the generated XML is as expected.

    private function buildElement(array &$addTo, array $elements)
    {
        if (0 === count($elements)) {
            return;
        }
        $element = array_shift($elements);
        $addTo[$element] = array();
        $this->buildElement($addTo, $elements);
        return;
    }


Test script:
---------------
<?php
class Example
{
    private function buildElement(array &$addTo, array $elements)
    {
        $previous = & $addTo;
        foreach ($elements as $element) {
            $previous[$element] = array();
            $previous = & $previous[$element];
        }
    }

    public function getSoapData()
    {
        $soapData = array();
        $this->buildElement($soapData, array('element1', 'element2', 'element3', 'element4', 'foo'));
        $soapData['element1']['element2']['element3']['element4']['element4']['foo'] = 'bar';
        return $soapData;
    }
}

$client = new SoapClient("some.wsdl");
$data = (new Example())->getSoapData();
$client->doSomething($data);

Expected result:
----------------
The XML sent to our supplier looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Body>
    <element1>
        <element2>
          <element3>
              <element4>
                <foo>bar</foo>
              </element4>
          </element3>
        </element2>
    </element1>
</SOAP-ENV:Body>

Actual result:
--------------
The XML sent to our supplier looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Body>
    <element1/>
</SOAP-ENV:Body>