Add node to existing XML file

Question

Here's my current XML file (books.xml):

<?xml version="1.0"?>
<books>
    <book>
        <isbn>123456789098</isbn>
        <title>Harry Potter</title>
        <author>J K. Rowling</author>
        <edition>1</edition>
    </book>
</books>

Please note that in this case, the edition is a number from 1 to 99, and that the ISBN has a length of 12 digits, contrary to the real-world concept of the book attribute.

I have an "add book" form and I want to save the collected data from that form (using post) by appending the new book to the already-existing XML file. What would be the best way to do this, in PHP? I am confused as to how to do it because the way I did it works half and half: either it saves an empty node or does nothing at all.

/*************************************
*code snippet of results.php
*************************************/
$doc = new DOMDocument();
$doc->load('books.xml');
$nodes = $doc->getElementsByTagName('books');
if($nodes->length > 0)
{
    $b = $doc->createElement( "book" );
    $isbn = $doc->createElement( "isbn" );
    $isbn->appendChild(
    $doc->createTextNode( $book['isbn'] ));
    $b->appendChild( $isbn );

    $title = $doc->createElement( "title" );
    $title->appendChild(
    $doc->createTextNode( $book['title'] ));
    $b->appendChild( $title );

    $author = $doc->createElement( "author" );
    $author->appendChild(
    $doc->createTextNode( $book['author'] ));
    $b->appendChild( $author );

    $edition = $doc->createElement( "edition" );
    $edition->appendChild(
    $doc->createTextNode( $book['edition'] ));
    $b->appendChild( $edition );

    $doc->appendChild( $b );
  }
  $doc->save('books.xml');

Thank you for your help.

Musa · Accepted Answer · 2012-12-10 03:35:14Z

3

You need to append to the documentElement

$doc->documentElement->appendChild( $b );

Also you could use a document fragment to make your work easier

$fragment = $doc->createDocumentFragment();
$fragment->appendXML("    <book>
        <isbn>{$book['isbn']}</isbn>
        <title>{$book['title']}</title>
        <author>{$book['author']}</author>
        <edition>{$book['edition']}</edition>
    </book>
");
$doc->documentElement->appendChild($fragment);

http://codepad.org/xoK4kLs8

answered Dec 10, 2012 at 3:35

Musa

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3 Comments

Christopher Richa Over a year ago

Thank you for the prompt answer. I replaced my $doc->appendChild( $b ); line with your suggestion, $doc->documentElement->appendChild( $b );. However, I get an empty node. Have I missed something? I am allegedly adding text in these lines: $isbn = $doc->createElement( "isbn" );

Musa Over a year ago

@ChristopherRicha are you sure $book['isbn'], $book['edition'] etc aren't empty?

Christopher Richa Over a year ago

Actually, never mind. I figured it out. Just a syntax error in creating my array. Thank you tons! I was creating my array as $book[0]['isbn'], etc. when it should have been simply $book['isbn'].

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