title: Laravel Eloquent unique() - Seems to not work
body: <p>I'm using Laravel Eloquent to pick out unique answers.</p>
  
  <p>So in my Database I have 3 answers, But they are under two different questions.</p>
  
  <p>So all I would need returning back is the number 2, Not the number 3.</p>
  
  <p>My code so far is :</p>
  
  <pre><code>$foundation_scores = Foundation::where('user_id', $this-&gt;user_id)
                                         -&gt;where('foundation_section', 'theory')
                                         -&gt;get();
  
          $foundation_scores-&gt;unique('foundation_question');
          $foundation_scores = count($foundation_scores);
  </code></pre>
  
  <p>The unique('foundation_question') is returning <strong>3</strong>. It should return <strong>2</strong></p>
  
  <p>Any ideas why this would be?</p>
  
  <p>My collection looks as follows (NOTE) I've outputted it as an array to avoide all the code Laravel Returns :</p>
  
  <pre><code>array:3 [
    0 =&gt; array:12 [
      "foundation_id" =&gt; 3
      "user_id" =&gt; 17019
      "foundation_section" =&gt; "theory"
      "unit_id" =&gt; 0
      "foundation_sub_section" =&gt; "Unit 1"
      "foundation_question" =&gt; 0
      "foundation_reference" =&gt; "Ref one way st"
      "foundation_answer" =&gt; "Ref answer st"
      "created_at" =&gt; "2017-10-25 11:57:05"
      "updated_at" =&gt; "2017-10-25 11:57:05"
      "deleted_at" =&gt; null
      "friendly_date" =&gt; "25th October 2017"
    ]
    1 =&gt; array:12 [
      "foundation_id" =&gt; 4
      "user_id" =&gt; 17019
      "foundation_section" =&gt; "theory"
      "unit_id" =&gt; 0
      "foundation_sub_section" =&gt; "Unit 1"
      "foundation_question" =&gt; 0
      "foundation_reference" =&gt; "Red"
      "foundation_answer" =&gt; "Ans"
      "created_at" =&gt; "2017-10-25 12:02:01"
      "updated_at" =&gt; "2017-10-25 12:02:01"
      "deleted_at" =&gt; null
      "friendly_date" =&gt; "25th October 2017"
    ]
    2 =&gt; array:12 [
      "foundation_id" =&gt; 5
      "user_id" =&gt; 17019
      "foundation_section" =&gt; "theory"
      "unit_id" =&gt; 0
      "foundation_sub_section" =&gt; "Unit 1"
      "foundation_question" =&gt; 1
      "foundation_reference" =&gt; "XY"
      "foundation_answer" =&gt; "Z"
      "created_at" =&gt; "2017-10-25 12:02:19"
      "updated_at" =&gt; "2017-10-25 12:02:19"
      "deleted_at" =&gt; null
      "friendly_date" =&gt; "25th October 2017"
    ]
  ]
  </code></pre>
  
  <p>Is their a bug with unique. Or is it something I'm doing wrong?</p>