PHP 'Hello World' Tutorial added

php/lesson1/tutorial.md

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+---
+layout: page
+title: Introduction to PHP
+---
+
+##### Requirements
+
+* 15 minutes
+* PHP installed - this is by default on most Operating Systems. But if not, here are the official [installation instructions](http://php.net/manual/en/install.php)
+    * Check installation by running the following command in cli `php -v`, this should output the version, eg. **5.5.9**
+
+##### Achievements
+
+By the end of this tutorial you will be able to:
+
+* write a **Hello World** Application that outputs on the:
+    * Command Line (CLI)
+    * Browser
+
+---
+
+## What is PHP?
+
+From the **PHP** [website](http://php.net/manual/en/intro-whatis.php)
+
+> PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.
+
+Well what does this mean? It is very easy to build dynamic websites using **PHP** as the server-side language, which generates **HTML**.
+
+## What does PHP look like?
+
+A simple Hello World application would look like the following:
+
+*File: index.php*
+```php
+<?php
+echo "Hello World";
+```
+
+1. The file must end with the extension `.php`
+2. The file must begin with the opening tag `<?php`
+3. `"` are used to Open/Close a string
+4. 'echo' Outputs the string [echo on php website](http://php.net/manual/en/function.echo.php)
+
+## How to run the script?
+
+On the Command Line (CLI), type:
+
+```php
+php index.php
+```
+
+And the output will be:
+
+```bash
+$ php index.php
+Hello World
+```
+
+*Note: `$` implies the Command Line shell, you did not need to type this.*
+
+## How to the output in the browser?
+
+Seeing it on the Command Line is great, but what about the browser? We will need to get a WebServer running, the easiest way is to use the built-in PHP WebServer.
+
+*Note: Built-in PHP WebServer is great for Development, but **NOT** Production.*
+
+Go to the directory where you created the `index.php` file and run the following command:
+
+```bash
+$ php -S 0.0.0.0:8080
+```
+
+1. `php` is the same command from before, that we used to run our **php** script
+2. `-S` means built-in WebServer
+3. `0.0.0.0` is the IP that the WebServer should listen on. By using `0` it will listen on everything - fine for development
+4. `8080` is the port to listen on - fine for development but in production the default port is `80` and therefore not required when accessing a URL
+
+Lets see the script output in your web browser! In your web browser navigate to ` http://localhost:8080/` and you should see:
+
+![Hello World](assets/images/helloworld.png)
+
+## Summary
+
+Now you should know how to create a simple **PHP** script and run it via the Command Line or via the Built-in **PHP** WebServer and see the output to the Command Line or the Browser respectively.