simplexml_load_string loose the order of tags

I have the following XML:

<mobapp>    
    <form>
        <input type="text" name="target" id="target" value="" maxlength="8" required="true" pattern="[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]"/>
        <label for="target"> Phone number</label> 
        <input type="number" name="amount" id="amount" min="0" maxlength="16" required="true"/> 
        <label for="amount"> Amount to load:</label> 
    </form> 
</<mobapp>

When I use simplexml_load_string($theXML) I get the following:

object(SimpleXMLElement)#150 (3) {
  ["input"]=>
  array(2) {
    [0]=>
    object(SimpleXMLElement)#146 (1) {
      ["@attributes"]=>
      ...
    }
[1]=>
    object(SimpleXMLElement)#146 (1) {
      ["@attributes"]=>
      ...
    }
}
["label"]=>
  array(2) {
    [0]=> ...
[1]=> ...

}

( I removed all the attributes to make it simpler to understand)

So I get an array of 2 "input" and an array of 2 "label", but I don't know the order in which they were in the XML.

Is there a way to get that order?