To my knowledge such a program does not exist and will probably not ever exist.
PHP runs on the server.
It is used to do server-side stuff like dynamically generate websites.
Where as tools like Frontpage just edit static web pages.
In a sense PHP is a competitor to products like Frontpage.
For example you might use PHP to insert a navigation bar on the top of each on of your pages. However the navigation bar in PHP has no PHP directly behind it -- it has html behind it.
It may be implemented in a number of ways, as PHP is Turing-complete.
- Possibly the whole overall site is each page slotted into a template written in PHP, that includes the header.
- Possibly each individual page has instructions in it to read a HTML snippet (describing the header) from a file and insert after the tag.
- Possibly the PHP is more clever, maybe it is generating different HTML for the headers depending on which page it is generating (e.g. the current section may be in bold).
A subsection of a web page won't really have PHP behind it so much as the PHP page (on the server) with have HTML with in it.
Some subsets of uses of PHP might be able to be thought of (/set up) this way,
however you would be limiting yourself to a small subset of the true capacity of PHP.
If you want to learn PHP, then learn PHP, and that is going to involve editing raw text files.
Better yet, consider not learning PHP. It is not fantastic. If you are making something new (rather than learning to support something legacy), consider the plethora of modern web frameworks like Ruby-on-Rails, or Python's Django.
For more information you might like to read this.