Dropdown list box using data from XML file

<?Php
$obj_xml = new SimpleXMLElement('file-xml-demo.xml', NULL, TRUE);
// Total number of elements present ///
//$total = $obj_xml->count(); // total number of elements for PHP 5.3 and above
$total =count($obj_xml->children());  // for < php 5.3 version

$str="<select name='student'>";
for($i=0; $i<$total; $i++) { 
$str= $str . "<option value=".$obj_xml->details[$i]->id.">".$obj_xml->details[$i]->name. "</option>";
}
$str = $str. "</select>";
echo $str;
?>