Edit xml from php

[biggipsy]

Good Morning

 

I have one doubt , i need edit xml from php

if i have the following code

 

$a = $xml->no [1];

 

i get the "no" in line 1

 

but i want edit the line from a variable:

 

Example (dont work)

 

$linha = $_GET['linha'];

 

$a = $xml->no [$linha];

 

How I can edit the line?