PHP add, delete

I am trying to add and delete data from an XML file using PHP. The addition works, but when I try to delete, the element is not removed from Training.xml. No error appears, it just doesn't do anything. What is the reason and how can I fix it?

<?php $name = $_POST['Name']; $email = $_POST['Email']; $major = $_POST['Major']; $xml = new DOMDocument(); $xml->load('Training.xml'); $root = $xml->getElementsByTagName('trainers')->item(0); $trainer = $xml->createElement('trainer'); $trainer->appendChild($xml->createElement('Name', $name)); $trainer->appendChild($xml->createElement('Email', $email)); $trainer->appendChild($xml->createElement('Major', $major)); $root->appendChild($trainer); $xml->save('Training.xml'); ?> <?php $index = (int)$_POST['index']; $xml = new DOMDocument(); $xml->load('Training.xml'); $trainers = $xml->getElementsByTagName('trainer'); $trainer = $trainers->item($index); $trainer->parentNode->removeChild($trainer); $xml->save('Training.xml'); echo "Delete Successfully "; ?>