<?php
$xmlstring = "<parent><child> hello world </child></parent>";
$xml = simplexml_load_string($xmlstring);
$foo = array( (string) $xml->child );
var_dump($xml).PHP_EOL;
var_dump($foo);
?>

object(SimpleXMLElement)#1 (1) {
  ["child"]=>
  string(13) " hello world "
}
array(1) {
  [0]=>
  string(13) " hello world "
}