You can parse XML from a string or from a XML file

1. From a string

$xml_obj = simplexml_load_string($string);

2. From a file

$xml_obj = simplexml_load_file('books.xml');

Example of parsing

Considering the following XML:

<?xml version="1.0" encoding="UTF-8"?>
<books>
   <book>
      <name>PHP - An Introduction</name>
      <price>$5.95</price>
      <id>1</id>
   </book>
   <book>
      <name>PHP - Advanced</name>
      <price>$25.00</price>
      <id>2</id>
   </book>
</books>

This is a example code to parse it

$xml = simplexml_load_string($xml_string);
$books = $xml->book;
foreach ($books as $book) {
    $id = $book->id;
    $title = $book->name;
    $price = $book->price;
    print_r ("The title of the book $id is $title and it costs $price." . "\\n");
}

This will output:

The title of the book 1 is PHP - An Introduction and it costs $5.95. The title of the book 2 is PHP - Advanced and it costs $25.00.