Reading and writing XML DOM with PHP_PHP tutorial

There are many techniques for reading and writing XML in PHP. This article provides three ways to read XML: using a DOM library, using a SAX parser, and using regular expressions. Writing XML using DOM and PHP text templates is also covered.

Reading and writing Extensible Markup Language (XML) with PHP may seem a little scary. In fact, XML and all its related technologies can be scary, but reading and writing XML in PHP doesn't have to be a scary task. First, you need to learn a little bit about XML—what it is and what you can do with it. Then, you need to learn how to read and write XML in PHP, and there are many ways to do this.

This article provides a brief introduction to XML and then explains how to read and write XML with PHP.

​What is XML?

XML is a data storage format. It does not define what data is saved, nor does it define the format of the data. XML simply defines tags and the attributes of those tags. Well-formed XML markup looks like this:

＜name＞Jack Herrington＜/name＞

This tag contains some text: Jack Herrington.

An XML tag that does not contain text looks like this:

＜powerUp /＞

There is more than one way to write something in XML. For example, this tag forms the same output as the previous tag:

＜powerUp＞＜/powerUp＞

You can also add attributes to XML tags. For example, this tag contains first and last attributes:

＜name first="Jack" last="Herrington" /＞

You can also use XML to encode special characters. For example, the & symbol can be encoded like this:

&

An XML file containing tags and attributes, if formatted like the example, is well-formed, meaning the tags are symmetrical and the characters are encoded correctly. Listing 1 is an example of well-formed XML.

Listing 1. XML book list example

            ＜books＞
            ＜book＞
            ＜author＞Jack Herrington＜/author＞
            ＜title＞PHP Hacks＜/title＞
            ＜publisher＞OReilly＜/publisher＞
            ＜/book＞
            ＜book＞
            ＜author＞Jack Herrington＜/author＞
            ＜title＞Podcasting Hacks＜/title＞
            ＜publisher＞OReilly＜/publisher＞
            ＜/book＞
            ＜/books＞
            

The XML in Listing 1 contains a list of books. The parent tag contains a set of tags, each of which contains ,

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