If you don't want to translate the PHP code into C# then you must invoke the PHP interpreter.
First, look at the license on the PHP code you would be using. When I looked at the code earlier I noticed that all but one PHP file had a GNU GPL license on it. GNU GPL should work for what you want, but I recommend that you review the GNU GPL if you haven't done so already. You should also look into what license is supposed to be applied to the last file before continuing.
Second, rewrite the entry file. The file in question is upload_file.php. This file loads the other files as includes, parses the SC2 replay file, and generates an output for use by a web browser. You just need to rewrite this file to have it output a simplified version of its output to the console. You might have it receive the name of the replay file from command line arguments. The other files that are marked as GNU GPL can just be copied directly into your project. I should also say here that there may already be a console version. Take a minute to look around for one.
Third, write a C# application. Invoke the PHP interpreter telling it the what file to interpret, and the name of the replay file to parse. You will need to redirect the console output from your PHP instance into your C# code to be able to read the output.
Fourth, read the output.
Fifth, parse the output for use in your C# application.