PHP: How to force simplexml to use certain datatype for a node

How can one enforce simplexml_load_string( ) to use same data structure at each node point.

$xml = "
<level1>
  <level2>
    <level3>Hello</level3>
    <level3>stackoverflow</level3>
  </level2>
  <level2>
    <level3>My problem</level3>
  </level2>
</level1>";

$xmlObj = simplexml_load_string($xml)
var_dump($xmlObj);

Examining the output,

level1 is an object; level2 is an array; level2[0] is an array.

level2[1] is an object, because there's only one child node, which I'll rather have as a single index array.

I'm collecting the xml from user, and there may be 1 or more nodes inside each level2. My sanitisation block is a foreach loop which fails when there's only one node inside level2.

The sanitation block looks something like this

foreach($xmlObj -> level2 as $lvl2){
  if($lvl2 -> level3[0] == 'condition'){ doSomething( ); }
}

doSomething() works fine when <level2> always has more than one child node in the xml string. If <level2> has only one child <level3> node, an error about trying to get attribute of a non-object comes up.

var_dump shows that the data type changes from object to array depending on how many nodes are nested within.

I'll prefer a way to ensure <level2> to always be an array regardless of how many children are within. That saves me from editing too much. But any other way out would suffice.

Thanks

Solution

It is not an information available in the XML itself. So you will have to add it in your implementation. SimpleXML provides both list and item access to a child elements. If you access it as a list (for example with foreach) it will provide all matching child elements.

$xml = "
<level1>
  <level2>
    <level3>Hello</level3>
    <level3>stackoverflow</level3>
  </level2>
  <level2>
    <level3>My problem</level3>
  </level2>
</level1>";

$level1 = new SimpleXMLElement($xml);

$result = [];
foreach($level1->level2 as $level2) {
    $data2 = [];
    foreach ($level2->level3 as $level3) {
        $data2[] = (string)$level3;
    }
    $result[] = $data2;
}

var_dump($result);

So the trick is to use the SimpleXMLElement instance directly and not convert it into an array. Do not treat the creation of your JSON structure as a generic conversion. Build up a specific output while reading the XML using SimpleXML.