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    <blockquote> <p><sub>I don't know where you leaned about the DI, but the resources seem quite questionable. Instead you should begin by watching <a href="http://www.youtube.com/watch?v=RlfLCWKxHJ0" rel="nofollow">this lecture</a>, followed by <a href="http://martinfowler.com/articles/injection.html" rel="nofollow">article</a> from <em>Martin Fowler</em>. Maybe supplemented by <a href="http://blog.ircmaxell.com/2013/01/dependency-injection-programming-with.html" rel="nofollow">this</a> short video.</sub></p> </blockquote> <pre><code>class Container { protected $db; public static newPhoto() { $photo = new Photo; $photo-&gt;setDB(static::$db); $photo-&gt;setConfig(); $photo-&gt;setResponse(); return $photo; } } $photo = Container::newPhoto(); </code></pre> <p>This is not implementing dependency injection. It actually is just an example of poorly implemented static factory method (anti)pattern. Especially the magical methods <code>$photo-&gt;setConfig()</code> and <code>$photo-&gt;setResponse()</code> which apparently do some work, but receive no parameters.</p> <p>And then there is this code:</p> <pre><code>class Photo { protected $db; protected $config; protected $response; public function __construct($dbConn=null,$config='123',$response=true) { if(is_null($dbConn)) $this-&gt;db = DB::getInstance(); else $this-&gt;db = $dbConn; ...etc } } $photo = new Photo($dbConn); </code></pre> <p>Instead of just assigning values, you decide to hide the dependencies of it, and, if they are not provided, to take them from global scope. And of course, your constructor ends up containing quite a log of computation. Thus making it untestable.</p> <p>Oh .. and then there is the magical boolean value. Whenever where is such a parameter assigned to a class in constructor, it is a clear sign that you actually needed two different classes, which implement same interface. </p> <p>So.. to answer your question:</p> <blockquote> <p>I've been reading about Dependency Injection but the examples I've found just look like bad code to me, so my main question is am I right in thinking it is bad code, or am I misunderstanding the purpose of it, and is my example any better?</p> </blockquote> <p>No. Your example is not better. You just combined the worst parts from both your earlier code example in single class definition.</p>
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    1. COGenuinely thank you. I have looked at a few places but the example I got was from [Nettuts+](http://net.tutsplus.com/tutorials/php/dependency-injection-huh/) which seemed trustworthy, that's why I was so confused because it seemed so bad. I dont understand this though: 'you decide to hide the dependencies of it' - it seemed to me that I was not hiding them because I could do `$photo = new Photo($dbConn,$config,$response);` whilst retaining the default values that are provided by the first example. Better to leave out and empty the construct? What would you do in this situation for proper DI?
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    2. COFirst of all, there `$response` parameter should not even be there. It is a *FLAG*. It would select for two different behaviors. Instead, you should have two polymorphic classes, or extract that behavior to the class which uses `Photo`. Watch the lecture (and others from same series), they will explain some of the issues there.
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    3. COAs for constructor's parameters. It is ok to have default values for the,. But "what to do" which such situation should not be handles in constructor. If you see that you class needs to be "prepared" before it becomes available in the rest of the code, then use a `Builder` for it, which would then call `prepare()` or `init()` method in the created instance. Thing is, that in this example the DB connection is **mandatory**. Your class cannot function without it. You should not even need to do any checks here. If DB instance is not provides, it is a fatal error.
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