ساخت فایل xml با پی اچ پی

<?php
class Xml_writer extends XMLWriter
{
    private $_rootName = '';
    private $_xmlVersion = '1.0';
    private $_charSet = 'UTF-8';
    private $_indentString = '    ';
    private $_xsltFilePath = '';

    public function __construct ()
    {}
    public function setRootName ($rootName)
    {
        $this->_rootName = $rootName;
    }
    public function setXmlVersion ($version)
    {
        $this->_xmlVersion = $version;
    }
    public function setCharSet ($charSet)
    {
        $this->_charSet = $charSet;
    }
    public function setIndentStr ($indentString)
    {
        $this->_indentString = $indentString;
    }
    public function setXsltFilePath ($xsltFilePath)
    {
        $this->_xsltFilePath = $xsltFilePath;
    }
    public function initiate ()
    {
        $this->openMemory();
        if ($this->_indentString) {
            $this->setIndent(true);
            $this->setIndentString($this->_indentString);
        }
        $this->startDocument($this->_xmlVersion, $this->_charSet);
        if ($this->_xsltFilePath) {
            $this->writePi('xml-stylesheet', 'type="text/xsl" href="' . $this->_xsltFilePath . '"');
        }
        $this->startElement($this->_rootName);
    }
    public function startBranch ($name, $attributes = array())
    {
        $this->startElement($name);
        $this->_addAttributes($attributes);
    }
    public function endBranch ()
    {
        $this->endElement();
    }
    public function addNode ($name, $value, $attributes = array(), $cdata = false)
    {
        if ($cdata) {
            $this->startElement($name);
            $this->_addAttributes($attributes);
            $this->writeCdata($value);
            $this->endElement();
        }
        else {
            $this->startElement($name);
            $this->_addAttributes($attributes);
            $this->text($value);
            $this->endElement();
        }
    }
    public function getXml ($echo = false)
    {
        if ($echo == true) {
            header('Content-type: text/xml');
        }
        $this->endElement();
        $this->endDocument();
        $output = $this->outputMemory();
        if ($echo == true) {
            print $output;
        }
        return $output;
    }
    private function _addAttributes ($attributes)
    {
        if (count($attributes) > 0) {
            foreach ($attributes as $key => $value) {
                $this->writeAttribute($key, $value);
            }
        }
    }
}
?>

<?php

require_once("xmlWriter.php");
$xml = new Xml_writer;
$xml->setRootName('Student');
$xml->initiate();

$xml->startBranch("person");
$xml->addNode("firstName", "Amir");
$xml->addNode("lastName", "Shokri");
$xml->endBranch();

$xml->startBranch("person");
$xml->addNode("firstName", "John");
$xml->addNode("lastName", "Due");
$xml->endBranch();

$file_name = "myxmlfile.xml";
$myxmlfile = fopen($file_name, "w");
fwrite($myxmlfile, $xml->getXml(false));
fclose($myxmlfile);


?>