PHP XML Expat

The built-in XML Expat Parser makes it possible to process XML documents in PHP.

To read and update - create and process - an XML document, you need an XML parser.

There are two basic types of XML parsers:

• Tree-based parser: This parser transforms an XML document into a tree structure. It analyzes the entire document, and provides access to the elements in the tree, such as the Document Object Model (DOM).
• Event-based parser: The XML document as a series of events. When a specific event occurs, the parser will call the function to process.

Expat parser is event-based parser.

Event-based parser focus on the content of an XML document, rather than their structure. Because of this, event-based parser can access data faster than tree-based parser.

Look at the following XML fraction:

An event-based parser reports the XML above as a series of three events:

• Start element: from
• Start CDATA section, value: Jani
• Close element: from

The XML Expat Parser functions are part of the PHP core. There is no installation needed to use these functions.

The XML file "note.xml" will be used in the example below:

Output :

  -- Note --
To: Tove
From: Jani
Heading: Reminder
Message: Don't forget me this weekend!
 

Example explained:

• Initialize the XML parser with the xml_parser_create() functionCreate functions to use with the different event handlers
• Add the xml_set_element_handler() function to specify which function will be executed when the parser encounters the opening and closing tags
• Add the xml_set_character_data_handler() function to specify which function will execute when the parser encounters character data
• Parse the file "note.xml" with the xml_parse() function
• In case of an error, add xml_error_string() function to convert an XML error to a textual description
• Call the xml_parser_free() function to release the memory allocated with the xml_parser_create() function