How to convert array to SimpleXML

<?php

/**
 * Modified http://stackoverflow.com/a/5965940/1113356, Answer
 */

header('Content-Type: text/xml');

$student_info[] = array(
    'id'       =>  '001',
    'name'     =>  'Mifas',
    'subjects' => array('English','Maths','IT')
);

$student_info[] = array(
    'id'    =>  '002',
    'name'  =>  'Ijas',
    'subjects'  => array('Science','History','Social')

);

// creating object of SimpleXMLElement
$xml_student_info = new SimpleXMLElement("<?xml version=\"1.0\"?><student_info></student_info>");

// function call to convert array to xml
array_to_xml($student_info,$xml_student_info);

//saving generated xml file
print $xml_student_info->asXML();


// function defination to convert array to xml
function array_to_xml($student_info, &$xml_student_info) {
    foreach($student_info as $key => $value) {
        if(is_array($value)) {
            $key = is_numeric($key) ? "item$key" : $key;
            $subnode = $xml_student_info->addChild("$key");
            array_to_xml($value, $subnode);
        }
        else {
            $key = is_numeric($key) ? "item$key" : $key;
            $xml_student_info->addChild("$key","$value");
        }
    }
}