Xml Append/Add new node php - php

Question

I'm trying to update and add node to a xml file. Currently I can create and overwrite the file with my new node, however what I need to do is do to is add the new node to the existing file (.xml) and I am exhausted. I am new to php (I've tried all every code on this site and this is my current code can't be added here ... please Help
$doc = new DOMDocument;
// Load the XML
///$doc->loadXML("<root/>");
//---- ///$xml = new Document;
///$xml ->loadXML($xml);
//$xml = simplexml_load_file("pole.xml");
$title = $_POST["title"];
$xml = <<<XML <item> <title>$title</title> </item> XML;
$xml = new Document;
$xml ->loadXML($xml);
$xml ->appendXML($xml);
$xml = new SimpleXMLElement($xml);
echo $xml->saveXML('pole.xml');

Answer 1

I can offer no advice for using SimpleXML but as the above does attempt at using DOMDocument perhaps the following simple example will be of use.
$filename='pole.xml';
# Stage 1
# -------
// Create an instance of DOMDocument and then
// generate whatever XML you need using DOMDocument
// and save.
libxml_use_internal_errors( true );
$dom=new DOMDocument('1.0','utf-8');
$dom->formatOutput=true;
$dom->preserveWhiteSpace=true;
$root=$dom->createElement('Root');
$dom->appendChild( $root );
$item=$dom->createElement('Item');
$title=$dom->createElement('title','Hello World');
$item->appendChild( $title );
$root->appendChild( $item );
$dom->save( $filename );
$dom=null;
This yields the following XML:
<?xml version="1.0" encoding="utf-8"?>
<Root>
<Item>
<title>Hello World</title>
</Item>
</Root>
To then modify the XML file you have created or downloaded etc:
# Stage 2
# -------
// A new instance of DOMDocument is NOT strictly necessary here
// if you are continuing to work with the generated XML but for the purposes
// of this example assume stage 1 and stage 2 are done in isolation.
// Find the ROOT node of the document and then add some more data...
// This simply adds two new simple nodes that have various attributes
// but could be considerably more complex in structure.
$dom=new DOMDocument;
$dom->formatOutput=true;
$dom->preserveWhiteSpace=false;
$dom->load( $filename );
# Find the Root node... !!important!!
$root=$dom->getElementsByTagName('Root')->item(0);
# add a new node
$item=$dom->createElement('Banana','Adored by monkeys');
$attributes=array(
'Origin' => 'Central America',
'Type' => 'Berry',
'Genus' => 'Musa'
);
foreach( $attributes as $attr => $value ){
$attr=$dom->createAttribute( $attr );
$attr->value=$value;
$item->appendChild( $attr );
}
#ensure that you add the new node to the dom
$root->appendChild( $item );
#new node
$item=$dom->createElement('Monkey','Enemies of Bananas');
$attributes=array(
'Phylum' => 'Chordata',
'Class' => 'Mammalia',
'Order' => 'Primates'
);
foreach( $attributes as $attr => $value ){
$attr=$dom->createAttribute( $attr );
$attr->value=$value;
$item->appendChild( $attr );
}
$root->appendChild( $item );
$dom->save( $filename );
$dom=null;
This modifies the XML file and yields the following:
<?xml version="1.0" encoding="utf-8"?>
<Root>
<Item>
<title>Hello World</title>
</Item>
<Banana Origin="Central America" Type="Berry" Genus="Musa">Adored by monkeys</Banana>
<Monkey Phylum="Chordata" Class="Mammalia" Order="Primates">Enemies of Bananas</Monkey>
</Root>