Parsing extremely large XML files in php

Question

I need to parse XML files of 40GB in size, and then normalize, and insert to a MySQL database. How much of the file I need to store in the database is not clear, neither do I know the XML structure.

Which parser should I use, and how would you go about doing this?

Answer 1

In PHP, you can read in extreme large XML files with the XMLReader^Docs:

$reader = new XMLReader();
$reader->open($xmlfile);

Extreme large XML files should be stored in a compressed format on disk. At least this makes sense as XML files have a high compression ratio. For example gzipped like large.xml.gz.

PHP supports that quite well with XMLReader via the compression wrappers^Docs:

$xmlfile = 'compress.zlib://path/to/large.xml.gz';

$reader = new XMLReader();
$reader->open($xmlfile);

The XMLReader allows you to operate on the current element "only". That means it's forward-only. If you need to keep parser state, you need to build it your own.

I often find it helpful to wrap the basic movements into a set of iterators that know how to operate on XMLReader like iterating through elements or child-elements only. You find this outlined in Parse XML with PHP and XMLReader.

See as well:

• PHP open gzipped XML