function xmlToArray($xml,$ns=null){
$a = array();
for($xml->rewind(); $xml->valid(); $xml->next()) {
$key = $xml->key();
if(!isset($a[$key])) { $a[$key] = array(); $i=0; }
else $i = count($a[$key]);
$simple = true;
foreach($xml->current()->attributes() as $k=>$v) {
$a[$key][$i][$k]=(string)$v;
$simple = false;
}
if($ns) foreach($ns as $nid=>$name) {
foreach($xml->current()->attributes($name) as $k=>$v) {
$a[$key][$i][$nid.':'.$k]=(string)$v;
$simple = false;
}
}
if($xml->hasChildren()) {
if($simple) $a[$key][$i] = xmlToArray($xml->current(), $ns);
else $a[$key][$i]['content'] = xmlToArray($xml->current(), $ns);
} else {
if($simple) $a[$key][$i] = strval($xml->current());
else $a[$key][$i]['content'] = strval($xml->current());
}
$i++;
}
return $a;
}

$xml = new SimpleXmlIterator(‘./a.xml’, null, true);
$namespaces = $xml->getNamespaces(true);
$arr = xmlToArray($xml,$namespaces);