php和xpath - 循环遍历特定元素的子元素

Question

I would like to loop through each book_list in the following xml file and for each book_list loop through each book for that book_list.

<inventory>
    <book_list>
        <book>
            <author>Rowling</author>
            <title>Harry Potter</title>
        </book>
        <book>
            <author>Blyton</author>
            <title>Famous 5</title>
        </book>
    </book_list>
    <book_list>
        <book>
            <author>Bloggs</author>
            <title>Learning XML</title>
        </book>
        <book>
            <author>Jones</author>
            <title>Beginning PHP</title>
        </book>
    </book_list>
</inventory>

How can I, for each book_list, loop through each book, using xpath in a php simplexml script? Here is my code,

$booklistpath = $xml->xpath('//booklist');

foreach ($booklistpath as $booklist) {
    $bookpath = $xml->xpath('//book');
    foreach ($bookpath as $book) {
        ...
    }
}

The first loop is fine, it goes through each book_list - but the nested loop, which is meant to go through each book for that particular book_list goes through each book in the entire document. I have also tried :-

'.//book'  and 
'descendant::book'

Answer 1

That's the right result since you're using the second xpath call on the original $xml which is the SimpleXMLElement for your whole XML document.

To get the books for each booklist just iterate them as follow:

$booklists = $sxe->xpath('//book_list');

foreach ($booklists as $booklist) {
    foreach ($booklist->book as $book) {
        echo $book->asXML();
    }
}