Added coding standards by request of @sekjun9878. Fixed #949 [gh#949]

CONTRIBUTING.md

@@ -20,8 +20,53 @@ Before contributing to PocketMine-MP, please read this.
 * Use the [Pull Request](https://github.com/PocketMine/PocketMine-MP/pull/new) system, your request will be checked and discussed.
 * __Create a single branch for that pull request__
 * If you want to be part of PocketMine-MP, we will ask you to.
-* Code using the syntax as in PocketMine-MP.
+* Code using the syntax as in PocketMine-MP. See below for an example.
 * The code must be clear and written in English, comments included.
 
 
 __Thanks for contributing to PocketMine-MP!__
+
+
+
+#### Code syntax
+
+It is mainly [PSR-2](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-1-basic-coding-standard.md) with a few exceptions.
+* Opening braces MUST go on the same line.
+* `else if` MUST be written as `elseif`. _(It is in PSR-2, but using a SHOULD)_
+* Control structure keywords or opening braces MUST NOT have one space after them.
+* Code MUST use tabs for indenting.
+* Long arrays MAY be split across multiple lines, where each subsequent line is indented once. 
+* Files MUST use only the `<?php` tag.
+* Files MUST NOT have an ending `?>` tag.
+* Code MUST NOT use namespaces. _(This restriction will be lifted on the Alpha_1.4 code)_
+* Strings SHOULD use the double quote `"` except when the single quote is required.
+* Arrays SHOULD be declared using `array()`, not the `[]` shortcut.
+* Argument lists MAY NOT be split across multiple lines, except long arrays.
+
+```php
+<?php 
+
+class ExampleClass{
+	const EXAMPLE_CLASS_CONSTANT = 1;
+	public $examplePublicVariable = "defaultValue";
+	private $examplePrivateVariable;
+	
+	public function __construct($firstArgument, &$secondArgument = null){
+		if($firstArgument === "exampleValue"){ //Remember to use === instead == when possible
+			//do things
+		}elseif($firstArgument === "otherValue"){
+			$secondArgument = function(){
+				return array(
+					0 => "value1",
+					1 => "value2",
+					2 => "value3",
+					3 => "value4",
+					4 => "value5",
+					5 => "value6",
+				);
+			}
+		}
+	}
+
+}
+```