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BlueM / XMLTransformer

Transforms XML (into XML, HTML, plaintext, …) using native PHP
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Overview

XMLTransformer is a PHP library for transforming any kind of input XML into an output string. This output string does not have to be XML, but can also be, for instance, HTML or plain text.

Transformations

XMLTransformer is able to …

When to use

In my opinion, XMLTransformer performs very well if the input XML and the output to be produced are similarly structured. Moreover, if data from the input XML has to be processed by an existing PHP codebase, it is possibly cleaner and simpler to use XMLTransformer instead of XSL-T.

When not to use

When the input data has to be re-arranged, you are probably better off with XSL-T, as this is something that XMLTransformer does not provide. (Although to some extent it can be done with appropriate callback code.) Of course you are free to combine XSL-T with XMLTransformer to get the best of both worlds, if one is not enough.

Installation

The recommended way to install this library is through Composer. For this, add "bluem/xmltransformer": "~2.0" to the requirements in your composer.json file. As the library uses semantic versioning, you will get fixes and feature additions, but not changes which break the API.

Alternatively, you can clone the repository using git or download an archived release.

Usage

You pass the input XML and the name of a callback function or a callback method (specified as usual, using [$object, 'methodName'] syntax) or an anonymous function / closure to XMLTransformer.

For each tag (opening, closing or empty) the callback function will be called with the tag’s name, its attributes and information on whether it is an opening, empty or closing tag. Now, your function / method / closure can return one of three things:

Callback function arguments

The callback function / method / closure is called with three arguments:

Please note that the attributes will always be given, even for a closing tag.

The transformation description array

When you wish to perform a transformation, you must return an associative array. In this case, the following keys can be used:

Additionally, for handling attributes, array keys in the form of “@” can be used, where is the attribute name (with namespaces, if not from the default namespace). The value of such an array key can be one of:

For instance, this return array …

return [
    XMLTransformer::RULE_TAG => 'demo',
    '@xml:id' => 'id',
    '@foo' => false,
    XMLTransformer::RULE_ADD_AFTER => '!',
];

… means:

Please note that (as XMLTransformer is not restricted to produce XML) no automatic escaping is done to values returned by the array. Only exception: attribute values, as XMLTransformer assumes that if you set attribute values, you want XML or HTML output.

Passing attributes by reference

The callback can accept the arguments’ array by reference, therefore allowing direct manipulation of the attributes. This can be handy when changing or removing a large number of attributes or when only a prefix or suffix (or namespace) of attributes’ names is known in advance.

See below for an example.

Examples

All of the examples below assume that your code includes the usual boilerplate code for Composer autoloading:

require 'vendor/autoload.php';

Hello world

use BlueM\XMLTransformer;

echo XMLTransformer::transformString(
    '<root><element>Hello world</element></root>',
    function($tag, $attributes, $opening) {
        return [
            XMLTransformer::RULE_TAG => false, // <-- Removes tag, but keeps content
        ];
    }
);
// Result: “Hello World”.

Multilingual Hello world

use BlueM\XMLTransformer;

function transform($tag, $attributes, $opening) {
    if ('hello-world' == $tag) {
        if (isset($attributes['xml:lang']) and
            'de' == $attributes['xml:lang']) {
            $str = 'Hallo Welt';
        } else {
            $str = 'Hello world';
        }
        return [
            XMLTransformer::RULE_TAG => false, // <-- Remove the tag, keep content
            XMLTransformer::RULE_ADD_BEFORE => $str,  // <- Insert literal content
        ];
    }

    if ('root' == $tag) {
        // We do not want the enclosing <root> tags in the output
        return [XMLTransformer::RULE_TAG => false];
    }
}

echo XMLTransformer::transformString(
    '<root><hello-world xml:lang="de" /></root>',
    'transform'
);
// Result: “Hallo Welt”

echo XMLTransformer::transformString(
    '<root><hello-world xml:lang="en" /></root>',
    'transform'
);
// Result: “Hello world”

Removing tags including all of their content

echo XMLTransformer::transformString(
    '<root><remove>Hello </remove>World</root>',
        function($tag, $attributes, $opening) {
            switch ($tag) {
                case 'remove':
                    return false; // <-- Removes tag incl. content
                case 'root':
                case 'keep':
                    return [XMLTransformer::RULE_TAG => false]; // <-- Remove tag, keep content
                    break;
                default:
                    // Returning null is not necessary, as this
                    // is the default behaviour. It is equivalent
                    // to "Do not change anything."
                    return null;
            }
        }
);
// Result: “World”

Changing attribute values

echo XMLTransformer::transformString(
    '<root abc="def"></root>',
    function($tag, $attributes, $opening) {
        return [
            '@abc' => 'xyz'
        ];
    }
);
// Result: “<root abc="xyz"></root>”
// Please note that empty tags will always be returned with
// a space before the slash.

Adding, renaming and removing attributes

echo XMLTransformer::transformString(
    '<root xml:id="abc"><bla xml:id="def" blah="yes"/></root>',
    function($tag, $attributes, $opening) {
        return [
            '@foo' => 'bar', // Add attribute "foo" with value "bar"
            '@blah' => false, // Remove attribute "blah"
            '@xml:id' => '@id', // Rename attribute "xml:id" to "id"
        ];
    }
);
// Result: “<root id="abc" foo="bar"><bla id="def" foo="bar" /></root>”
// Please note that empty tags will always be returned with
// a space before the slash.

Modifying attributes by reference

echo XMLTransformer::transformString(
    '<root xml:a="a" xml:b="b" id="foo">Content</root>',
    function($tag, &$attributes, $opening) {
        foreach ($attributes as $name => $value) {
            if ('xml:' === substr($name, 0, 4)) {
                unset($attributes[$name]); // Drop attributes in "xml" namespace
            }
        }
    }
);
// Result: “<root id="foo">Content</root>”

Author & License

This code was written by Carsten Blüm (www.bluem.net) and licensed under the BSD2 license.

Version history

2.0.1 (2020-12-02)

2.0 (2018-02-12)

1.2 (2015-12-05)

1.1 (2015-08-15)

1.0 (2012-12-12)