Install php locally

of course, with IIS or apache

http://www.youtube.com/watch?v=Els0EDM1-So
http://www.youtube.com/watch?v=NEwII4TCagM&feature=related

If you are planning to use Apache then WAMP is also an option...

http://www.wampserver.com/en/ 

the wellknow : http://www.easyphp.org/fr/
or if you can, BUY this : http://www.nusphere.com/products/phped.htm

I'm actually using it for this application:

https://www.experts-exchange.com/questions/27291199/Use-php-to-get-a-photo-in-the-right-proportions.html

I'm manipulating .jpg files

Not sure which of the above would fit best for that.

Everything works fine on my web server, I just want to process the files locally.

So, I installed phpED, but I'm having trouble.

In Visual Basic, I usually issue the command:
WebBrowser1.Navigate ("http://website.com/myfile.php")

Now, since I have it local, I thought I could do:
WebBrowser1.Navigate ("C:/directory/myfile.php")

But it does not run the php, it simply displays it as a text file.

When you run the page, you've the url to use or choose an rxternal browser instead phped browser

https://www.experts-exchange.com/questions/27301706/Getting-phpED-to-work.html?cid=239&anchorAnswerId=36517432#a36517432

http://www.php.net/manual/en/features.commandline.php

php C:\directory\myfile.php

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This has spawned a new question:

https://www.experts-exchange.com/questions/27302647/Command-Line-PHP-variable.html