Why are elements in the XML document not being removed?

Question

PHP

Hello. I have a file with the following structure

<?xml version="1.0" encoding="utf-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>http://mysite.local/?title='Заголвоок 3'</loc>
    <lastmode>2014-12-27</lastmode>
    <priopity>0.6</priopity>
  </url>
  <url>
    <loc>http://mysite.local/?title='Заголвоок 3'</loc>
    <lastmode>2014-12-27</lastmode>
    <priopity>0.6</priopity>
  </url>
  <url>
    <loc>http://mysite.local/?title='Заголвоок 3'</loc>
    <lastmode>2014-12-27</lastmode>
    <priopity>0.6</priopity>
  </url>
  <url>
    <loc>http://mysite.local/?title='Заголвоок 3'</loc>
    <lastmode>2014-12-27</lastmode>
    <priopity>0.6</priopity>
  </url>
  <url>
    <loc>http://mysite.local/?title='Заголовок 0'</loc>
    <lastmode>2014-12-27</lastmode>
    <priopity>0.6</priopity>
  </url>
</urlset>

Task: remove all elements.
I decide:

<?php

  $dom = new DOMDocument('1.0', 'utf-8');
  $dom->formatOutput = true;
  $dom->preserveWhiteSpace = false;
  $dom->load("sitemap.xml");
  
  $sitemap = $dom->documentElement;
    
  $items = $sitemap->getElementsByTagName('url');
  foreach($items as $item)
  {
    $sitemap->removeChild($item);
  }
  $dom->save("sitemap1.xml");
?>

As a result, only 2 out of 5 elements are removed. Tell me where I made a mistake and what needs to be done to remove all elements?
Thank you in advance.

Answer 1

The foreach iterator pointer is placed on the element with index 0, then this element is removed, and the numbering shifts accordingly. The iterator jumps to the element at index 1, skipping the element at index 0.
You could do this:

while($items->length) {
    $sitemap->removeChild($items->item(0));
}

Answer 2

Use this loop

for($i = 0, $item = $items->item($i); $item; $item = $items->item($i)) {
    $sitemap->removeChild($item);
}

When you remove an element, you change the object, and foreach does not know about it