I just use Dreamweaver MX. For the display of the HTML page, it will show you the regular HTML view, and will show the script icon, or in the case of textbox content, will show the line of PHP code that fills the boxes value. Apart from this, there isn't much you can do for WYSIWYG PHP.
For actual visual aids in PHP development, Dreamweaver has built-in support for alot of PHP's functions so that it can highlight the syntax a little more intelligently for you. This is in the actual editing of the code though, and really has nothing to do with wysiwyg.
For reference, I tried a couple of other editors, and I still found that Dreamweaver worked best, especially considering the extra tools Dreamweaver has built-in (other scripting languages, automated components, and HTML wysiwyg editing), I think it's one of the better editors, even if it's not specifically for PHP.