I'll amend what I was saying earlier to say that there is one way of displaying a PHP file's source code, but it requires that the site in question have a weak script on it to begin with that can be exploited.
A PHP script can, for instance, open a file on the server, and then echo the contents to the page. If you find any sort of "raw" display type file that has a URL like w3.site.c0m/view.php?file=report.txt you can always try manually changing report.txt to target.php and see what that gets you.
Again, though, this is an incredible longshot, most sites simply won't have such a file waiting for you to exploit, and even if they do, good luck finding it in the first place.
One other thing to bear in mind: Just getting the PHP is likely not going to solve all of your problems. Most decent sites will have a large amount of stuff in the DB, so unless you have a strategy for getting the DB as well, just grabbing the PHP is not going to give you the keys to the kingdom. Instead, what it will give you, is a much better starting place for your outsourced team to build a knockoff.
Of course, there are still techniques for getting at a PHP file, but they are basically full on hacking, and really beyond the scope of BHW. If you really want to go down that road, do a search for "ethical hacking". Ethical hacking is basically white hat hacking, which probably sounds weak, but the truth is that the techniques that "ethical" hackers discuss are the same techniques that all the other hackers use. What makes them "ethical" is that they only use their mojo on sites that they have been hired to "test" for security flaws. The info you will get reading up on ethical hacking will be a goldmine of root access security holes, SQL injection attacks, arbitrary code execution attacks, and basically as much head turning security stuff as you could imagine.
Just remember though, if it were easy, everyone would be doing it.