After participating in several large-scale PHP projects and writing a lot of PHP code, I found that many tools can improve code quality and simplify publishing, making my life as a PHP developer much easier. Many of these tools are probably already in use by everyone. However, since some people don't even notice that these tools exist, I'll start with, well, without further ado, here is a list of tools that I think all PHP programmers should know. Phing - A project build system
Phing is a project build system based on Apache ANT. Its name is an acronym for a tongue-in-cheek statement - PHing Is Not GNU make. Phing can do everything a traditional build system like GNU make can do, without the steep learning curve.
The idea behind phing (and other build systems) is to evaluate a series of dependencies and then execute a series of PHP classes to correctly install and configure an application. The build process is controlled with a simple XML configuration file. Out of the box, phing has the built-in ability to perform a range of substitutions (such as changing include paths between your development and production versions), execute SQL statements, move and copy files, run external scripts, and more. You can also create your own custom tasks by extending the "task" class included in the distribution package.
Phing is an invaluable tool for anyone who needs to deploy large-scale PHP applications on more than one server. I also find it useful for simple PHP scripts.
Xdebug - debugging and analysis tool
Xdebug is a PHP extension that helps you debug and analyze scripts. The most useful features in Xdebug are the new attention, warning and error messages that are displayed when activated. If a script fails to run properly, Xdebug will output a full heap trace with the error message, along with the function name, parameter values, source file, and line number. This is a welcome feature for programmers who are tired of the poor error reporting capabilities that come with PHP by default.
This extension has many more advanced features that allow developers to perform code coverage analysis, collect analysis information and debug scripts interactively. The profiling functionality feature is particularly useful. The analyzer uses a common output file format, allowing you to quickly find bottlenecks in your code using tools like KCacheGrind. A good profiler is an essential tool for any serious developer, allowing you to properly optimize your code while avoiding the dangers of premature optimization.
PHPUnit - unit testing framework
PHPUnit is a lightweight PHP testing framework. It is a complete port of JUnit 3.8.1 under PHP5 and is a member of the xUnit family of test frameworks (they are based on the design of software pattern pioneer Kent Beck).
Unit testing is the foundation of several modern agile development methodologies, making PHPUnit a key tool for many large PHP projects. This tool can also be used by the Xdebug extension discussed earlier to generate code coverage reports, and can be integrated with phing to automate testing.
Propel - ORM (Object Relational Mapping) Framework
Propel is an object-relational mapping (ORM) framework under PHP5, which originated from the Apache Torque project. It provides a complex but easy-to-use database abstraction layer that allows you to use database entities in PHP just like ordinary classes and objects. Propel allows you to define your database using a simple XML format. This XML file is used to map the database and generate static classes used in the application.
Propel is built into the popular Symfony PHP framework (among others), which makes code more flexible, modular and portable. The project has excellent documentation, and a great support community.
phpMyAdmin / phpPgAdmin - web-based database management system
It has a long history but is still very useful. phpMyAdmin is one of the most useful management tools for any database (corresponding to PostgreSQL and SQLite are phpPgAdmin and phpSQLiteAdmin). It helps with everything - from creating and deleting databases for debugging applications to taking backups. Installing it is usually the first thing I do after installing Apache, PHP and MySQL on a LAMP server. If you use MySQL and somehow haven't heard of it, install it now.
Other Tools