php|architect's Guide to Web Scraping with PHP - Wind Business ...

Chapter 12
XMLReader Extension
The previous two chapters have covered two available XML extensions that implement
tree parsers. This chapter will focus on the XMLReader extension, which implements
a pull parser.
As mentioned in the chapter on the DOM extension, pull parsers differ from tree
parsers in that they read documents in a piecewise fashion rather than loading them
into memory all at once. A consequence of this is that pull parsers generally only
traverse documents once in one direction and leave you to collect whatever data is
relevant to you along the way.
Before getting started, a noteworthy point is that XMLReader’s underlying library,
libxml, uses UTF-8 encoding internally. As such, encoding issues will be mitigated
if any document you imported (particularly one that’s been cleaned using the tidy
extension) is encoded appropriately to avoid issues with conflicting encodings.
i
XML P a r s e r
The XML P a r s e r extension, as it is referred to in the PHP manual, is a predecessor
of XMLReader and an alternative for PHP 4 environments. Its API is oriented to a
more event-driven style of programming as opposed to the iterative orientation of
the XMLReader extension. F o r more information on the XML P a r s e r extension, see
http://php.net/manual/en/book.xml.php.