How to change the child elements of an xml tag with a specific attribute value?

Question

PHP

Let's put it this way: there is an xml file in which the following is written:

<main id="0">
    <name>Имя1</name>
    <fam>Фамилия1</fam>
</main>
<main id="1">
    <name>Имя2</name>
    <fam>Фамилия2</fam>
</main>

It is required to change the values ​​of only those tags whose id is equal to 1. Question: how to access child tags with a certain attribute value?
I use System.Xml

Answer 1

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Answer 2

Through XPath