I'm using the Netbeans IDE for PHP development for last 3-4 Months. There might be something better but for now Netbeans suffices my needs. Still I encourage you to seek alternatives. Perhaps you might get something better.
Now you must question : NetBeans is a Java IDE. So why use it for PHP? Well all I can say is that, because it supports PHP. And whatever support it provides is more than enough for me - at least as of now. So we install NetBeans Full Version which comes with all the goodies and also it has PHP support.
With Netbeans we have inherent support for a PHP project and we get templates to for various files. Also integrated is Symphony Framework and that one I'm yet to tinker with. We are also provided with PHP code clips through Tools > Palette > PHP Code Clips.
Using Projects window we can arrange the files in our Website as suits our need. We get tabs for multipple open files that makes navigation easier.
For CSS we get a style builder which lets us see the output and lists all parameters we can change. This makes working with CSS styles a breaze. For HTML we have autocompletion of end tags and syntax highlighting. Also is indentation which helps us keep track of blocks even in HTML.
the major shortcoming of Netbeans is its slow since it runs on Java. But still all above features coupled with the nice simple interface make Netbeans a very good IDE.
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