The Eclipse PHP Development Tools project (PDT) is the #1 open source PHP Integrated Development Environment (IDE). It has rapidly grown to be one of the most highly downloaded Eclipse projects. PDT provides an entry level IDE for with the basic code editing capabilities you need to get started with PHP development. PDT provides:
Basic PHP Editing with syntax highlighting and coloring
PDT is the foundation of Zend Studio the #1 commercial PHP IDE. Zend Studio Extends PDT with a number of high value additional features.
The simplest way to get started with PDT is to download a "all-in-one" build from the PDT download page. This package contains all the required Eclipse and PDT components in one simple easy to install package.
In addition you probably want a PHP Web server to run, test and debug your PHP with. This is where Zend Server comes in. If you are going to use a different web server you will either need XDebug to be installed or to get a copy of the Zend Web Debugger.
If you want you can also install PDT from plug-ins in the PDT the Eclipse update site. The package includes PDT and the Zend Executable Debugger Eclipse Plug-in. Note: The PHP plug-ins are included in the all-in-one package.