A simple list of tools for modern PHP development. There are alternatives to most of the tools, but I'll list native PHP tools wherever possible.

1. PHPUnit

PHPUnit is a testing framework belonging to the xUnit family of testing frameworks. Use it to write and run automated tests. Start using PHPUnit

2. Selenium RC

Selenium RC can be used in conjunction with PHPUnit to create and run automated tests within a web browser. It allows tests to be run on several modern browsers and is implemented in Java, making it available to different platforms. PHPUnit and Selenium

3. PHP CodeSniffer

PHP CodeSniffer is a PHP code tokenizer, that will analyse your code and report errors and warnings based on a set of Coding Standards. Documentation

4. Phing

Phing is a project build tool and is a PHP port of the popular Java program ant. Phing can be used to automate builds, database migration, deployment and configuration of code. Documentation. Database migrations with phing

5. Xdebug

Xdebug is a multi-purpose tool, providing remote debugging, stack traces, function traces, profiling and code coverage analysis. Debug clients are available in many PHP IDEs and even plugins so you can debug from everybody's favourite editor vim. Documentation

6. PHPDocumentor

PHPDocumentor is an automated documentation tool, that allows you to write specifically formatted comments in your code, that can be brought together to created API documentation. Tutorial

7. phpUnderControl

phpUnderControl is a patch for the popular Continuous Integration tool, CruiseControl. Together with the previous six tools, phpUnderControl gives you a great overview of the current state of your application/codebase. Keep an eye out for Xinc

8. Zend Framework - or <insert your favourite framework here>

Frameworks facilitate the development of software, by allowing developers to focus on the business requirements of the software, rather than the repetitive and tedious elements of development, such as caching. There are plenty of frameworks to choose from, but I particularly like the Zend Framework. Have a read through this excellent Getting started guide

9. Subversion

Subversion is a revision control system that has superceded CVS. If you're writing software of any kind, you shoud be using version control software.SVN Book

10. Jira

So I could have named one of many, but this is the one I've liked the most recently. Jira is a bug/issue tracking software package and can also help with project management in terms of goals and roadmaps. Most issue trackers link to version control repositories, such as Subversion. Only downside to Jira is that it costs for non open source projects.

I'm pleased to say that with a little bit of pushing and persuasion by myself, we are currently using all of these technologies with the exception of Jira, we have a bespoke issue tracker.

What do you think to the list? Anything I have missed? Any alternatives you prefer?