JSON and PHP

Guarav Arora has suggested a good article to read on the usage of JSON:

http://ditio.net/2008/07/17/php-json-and-javascript-usage/

Regular Expressions

Very useful article on using regular expressions for validation of different formats like usernames, email, phone numbers etc.

http://www.plentyofcode.com/2008/07/regular-expressions-for-username-date.html

Tutorials on the Zend Framework for PHP

A very nice collection of articles on the Zend Framework.

Zend Framework reviews, articles, tutorials, blogs and resources

Useful Articles on Programming

A collection of extremely useful articles on Programming. If possible, read all of them.

Useful articles and links
Useful articles and links 2
Useful articles and links 3
Useful articles and links 4
Useful articles and links 5

The Hitchhiker's Guide to PHP

A nice tutorial series on PHP from Oracle

The Hitchhiker's Guide to PHP

PHP vs J2EE vs ASP.Net

Some nice articles providing perspective on the three web application development languages:

J2EE vs ASP.NET vs PHP

PHP Vs ASP.net

PHP vs. ASP.NET Redux - Good article on Oracle

Testing Resources

A lot of testing resources are available on this page - http://testinghelp.googlepages.com/materials.