title: Laravel sort collection by date
body: <p>I have this collection result:</p>
  
  <pre><code>$result = [{
      "date": "2016-03-21",
      "total_earned": "101214.00"
  },
  {
      "date": "2016-03-22",
      "total_earned": "94334.00"
  },
  {
      "date": "2016-03-23",
      "total_earned": "96422.00"
  },
  {
      "date": "2016-02-23",
      "total_earned": 0
  },
  {
      "date": "2016-02-24",
      "total_earned": 0
  },
  {
      "date": "2016-02-25",
      "total_earned": 0
  }]
  </code></pre>
  
  <p>I want to sort the result by date:</p>
  
  <pre><code>$sorted = $transaction-&gt;sortBy('date')-&gt;values()-&gt;all();
  </code></pre>
  
  <p>But I don't get the expected result:</p>
  
  <pre><code>[{
      "date": "2016-02-23",
      "total_earned": 0
  
  },
  {
      "date": "2016-02-24",
      "total_earned": 0
  },
  {
      "date": "2016-02-25",
      "total_earned": 0
  },
  {
      "date": "2016-03-22",
      "total_earned": "94334.00"
  },
  {
      "date": "2016-03-21",
      "total_earned": "101214.00"
  },
  {
      "date": "2016-03-23",
      "total_earned": "96422.00"
  }]
  </code></pre>
  
  <p>As you can see all with month 2 is sort properly. However at month 3 it start messed up. (the real result is longer than this and it messed up start at month 3)</p>
  
  <p>Any solution to make it sort properly?</p>
  
  <p>Thanks.</p>