Append XML file under specified elemnt in PHP

Question

I have this XML file Book.xml:

<?xml version="1.0" encoding ="utf-8"?>
<School>
    <Class type="Math">
        <TITLE>Match 101</TITLE>
    </Class>

    <Class type="English">
        <TITLE>English 102</TITLE>
    </Class>

    <Students type="Secondary">
        <Student>
        </Student>
    </Students>

   <Grade>
   </Grade>

</School>

and want to add this XML file edit.xml under Student:

<Teachers>

</Teachers>

I am using PHP 8.1 and don't know how to do it?