initial commit

README.md

+# Dependency Injector
+
+A simple and lightweight dependency injector. You will need nothing more to tests your old legacy code.
+ 
+## What is a dependency
+
+Something that your script needs to work correct. For example an instance of `Calculator` or `Config`. Or even
+a class itself.
+
+## Examples
+
+### The `Config`
+```php
+<?php
+
+class Config {
+    private static $_instance;
+    
+    public $database = [
+        'host' => 'localhost',
+        'user' => 'john',
+        'password' => 'does.secret',
+        'database' => 'john_doe'
+    ];
+    
+    public $redis = ['host' => 'localhost'];
+    
+    private function __construct() {
+        // maybe some logic to change the config or initialize variables
+    }
+    
+    public static function getInstance() {
+        if (!self::$_instance) {
+            self::$_instance = new Config();
+        }
+        return self::$_instance;
+    }
+}
+
+class_alias('DependencyInjector', 'DI'); // create an alias for easier access
+
+DI::set('config', function() { return Config::getInstance(); });
+
+function someStaticFunction() {
+    // before
+    if (empty(Config::getInstance()->database['host'])) {
+        throw new Exception('No database host configured');
+    }
+    
+    // now
+    if (empty(DI::config()->database['host'])) {
+        throw new Exception('No database host configured');
+    }
+    
+    // or if you prefer
+    if (empty(DI::get('config')->database['host'])) {
+        throw new Exception('No database host configured');
+    }
+}
+```
+
+### The database connection
+```php
+<?php
+
+DI::set('database', function() {
+    $dbConfig = DI::config()->database;
+    
+    $mysql = new mysqli($dbConfig['host'], $dbConfig['user'], $dbConfig['password'], $dbConfig['database']);
+    
+    if (!empty($mysql->connect_error)) {
+        throw new Exception('could not connect to database (' . $mysql->connect_error . ')');
+    }
+    
+    return $mysql;
+});
+
+function someStaticFunction() {
+    // before it maybe looked like this
+    $mysql = MyApp::getDatabaseConnection();
+    
+    // now
+    $mysql = DI::database();
+    
+    $mysql->query('SELECT * FROM table');
+}
+```
+
+The problem before: you can not mock the call to `MyApp::getDatabaseConnection()`. You can still not mock the call to 
+`DI::database()` or `DI::get('database')`. But you can set the dependency to return a mock object:
+
+```php
+<?php
+
+class ApplicationTest extends PHPUnit_Framework_TestCase {
+    public function testSomeStaticFunction() {
+        $mock = $this->getMock(mysqli::class);
+        $mock->expects($this->once())->method('query')
+            ->with('SELECT * FROM table');
+        DI::set('database', function() use($mock) { return $mock; });
+            
+        someStaticFunction();
+    }
+}
+```