title: Filter Array Duplicates On Associative Value
body: <p>I've got an array:</p>
  
  <pre><code>(
  [0]
     (
        [room_num] =&gt; 1
        [is_event] =&gt; true
        [date] =&gt; '01/01/2013'
     )
  [1]
     (
        [room_num] =&gt; 2
        [is_event] =&gt; false
        [date] =&gt; ''
     )
  [2]
     (
        [room_num] =&gt; 3
        [is_event] =&gt; false
        [date] =&gt; ''
     )
  [3]
     (
        [room_num] =&gt; 1
        [is_event] =&gt; false
        [date] =&gt; ''
     )
  )
  </code></pre>
  
  <p>What I'd like to do is filter the results so that where <code>is_event = true</code> supersedes <code>is_event = false</code>. My returned array would look like:</p>
  
  <pre><code>(
  [0]
     (
        [room_num] =&gt; 1
        [is_event] =&gt; true
        [date] =&gt; '01/01/2013'
     )
  [1]
     (
        [room_num] =&gt; 2
        [is_event] =&gt; false
        [date] =&gt; ''
     )
  [2]
     (
        [room_num] =&gt; 3
        [is_event] =&gt; false
        [date] =&gt; ''
     )
  )
  </code></pre>
  
  <p>Sort of like array_unique except ON a certain value. </p>
  
  <p>Is there a built in function for this? </p>