Deserializing XML arrays with SimpleXML - php

Question

I need to deserialize some XML I receive into an object. I use SimpleXML to do this. An example of some of the XML received is this:
<?xml version="1.0" encoding="UTF-8"?>
<coupons type="array">
<coupon>
<coupon_code>baz</coupon_code>
<name>baz</name>
<discount_type>percent</discount_type>
<discount_percent type="integer">20</discount_percent>
<plan_codes type="array">
<plan_code>plus</plan_code>
<plan_code>pro</plan_code>
</plan_codes>
</coupon>
<coupon>
<coupon_code>test</coupon_code>
<name>Test</name>
<discount_type>dollars</discount_type>
<discount_in_cents>
<USD type="integer">2000</USD>
<EUR type="integer">1500</USD>
</discount_in_cents>
<plan_codes type="array">
<plan_code>plus</plan_code>
</plan_codes>
</coupon>
</coupons>
In this piece of XML, there are 3 types of arrays: <coupons> is an array of <coupon>. <coupon> has 2 arrays as well: <plan_codes> (which is a flat array) and <discount_in_cents> which is an associative array.
How does my deserializer work: I create a SimpleXMLElement from the XML and pass it to a function visitElement which takes a SimpleXMLElement and the type, array<Model\Coupon> in this case, indicating it's an array of Model\Coupon objects.
In my visitElement I check if the type is an existing class, if so, I create a new instance of that class and get a configuration for that Model, the configuration tells me which children need to be deserialized to which object variable. visitElement looks like this:
public function visitElement($element, $type)
{
// it is possible the element is not available
if (!$element) {
return null;
} else {
// get the value based on it's mapped type
switch ($type) {
case 'string':
return $this->visitString($element);
break;
// ...
// other cases
// ...
default: // catch other cases
if (class_exists($type)) {
// We mapped to an existing class
return $this->visitModel($type, $element);
} elseif ($this->isArrayType($type, $arrayType, $keepKey)) {
// We mapped to an array<type>
return $this->visitArray($arrayType, $element, $keepKey);
} else {
// A type we can't handle
return null;
}
}
}
}
This way, I have a nice recursive way of deserializing other XML as well, that might have nested objects (For example, the Account XML has an Address object nested within).
My Model\Coupon is configured so that <plan_codes> and <discount_in_cents> are considered array<string> and array<integer> respectively.
This is my visitArray function:
protected function visitArray($type, $element, $keepKey = false)
{
$value = null;
$i = 0;
foreach ($element->children() as $key => $child) {
$k = $keepKey ? $key : $i++;
$value[$k] = $this->visitElement($child, $type);
}
return $value;
}
This all works beautifully. I get an array of 2 Model\Coupon objects, with the second object having a discount_in_cents array that looks like ['USD' => 2000, 'EUR' => 1500], but it does NOT work for the plan codes...
When I var_dump those, I get
array (size=2)
0 => null
1 => null
and
array (size=1)
0 => null
Is there any reason why looping over <plan_codes> would yield different results/children than <coupons> or <discount_in_cents>?
At the moment, I implemented a workaround in visitArray as follows:
protected function visitArray($type, $element, $keepKey = false)
{
$value = null;
$i = 0;
foreach ($element->children() as $key => $child) {
$k = $keepKey ? $key : $i++;
$value[$k] = 'string' === $type ? (string)$child : $this->visitElement($child, $type);
}
return $value;
}