Added new phpunit/composer installation instructions

Author: martig7

_docs/developer/testing/install_php.md

@@ -23,6 +23,10 @@ If you are missing extensions you can install them with `PECL` which will be
 installed automatically with PHP, but you should have everything required by 
 default.
 
+### Windows
+
+Download [php 8.1](https://windows.php.net/download/) as a zip file under the thread safe category. Then extract the contents of the zip to a folder, and add the path to that folder to your path system variable. It's suggested that one extracts the contents of the zip to a folder called `php`, which can be put at `C:\php` for simplicity. You can then add `C:\php` to your path system environment variable.
+
 ------------- 
 
 Verify you have PHP installed correctly, submitty requires a version greater than 7.0

_docs/developer/testing/php_unit_tests.md

@@ -13,12 +13,27 @@ Before running PHP Unit Tests, you must install the required dependencies. You m
 ##### Inside the Vagrant VM
 
 1. Install [Composer](https://getcomposer.org/download/) through the command-line installation copy-paste.
-2. `cd` to `/usr/local/submitty/GIT_CHECKOUT/Submitty/site/`
+2. `cd` to `/usr/local/submitty/GIT_CHECKOUT/Submitty/site/`.
 3. run  `composer update`
 
 *Please be aware that many unit tests will not work inside the VM. It is suggested that you run tests individually.*
 
-##### On Your Local Machine
+##### On Mac
+
+1. Install [Composer](https://getcomposer.org/download/) using brew.
+2. `cd` to your `Submitty/site/` folder.
+3. run `composer install`
+
+##### On Windows (Not Suggested)
+
+1. Navigate to your php folder, and open the php configuration settings file.
+2. Ctrl-F and uncomment the line labelled `extension=fileinfo` (remove the semi-colon). Do the same for the line labelled `extension=sodium`.
+3. Install [Composer](https://getcomposer.org/download/), click the link labelled Composer-Setup.exe.
+4. Restart your terminal.
+5. `cd` to your `Submitty/site/` folder.
+6. Run `composer update`. If you are getting timeout errors, try using a VPN.
+
+*This is not a good way to run unit tests because many file paths will be broken. Like with the vagrant VM, it is suggested that you run tests individually.*
 
 ### Running PHP Unit Tests