title: Fill out missing dates into associative array
body: <p>What would be the simplest way to add missing dates in array like this?
  It needs to be in the correct order though &amp; since data can't be added in associative array with <code>array_slice()</code> I didn't find a way to do it without ending up with four foeach loops with converting into multidimensional array and converting back. Thanks!</p>
  
  <pre><code>    Array
  (
      [1.1.2016] =&gt; 10
      [3.1.2016] =&gt; 5
      [5.1.2016] =&gt; 8
      [8.1.2016] =&gt; 3
  )
  
  
  Array
  (
      [1.1.2016] =&gt; 10
      [2.1.2016] =&gt; 0
      [3.1.2016] =&gt; 5
      [4.1.2016] =&gt; 0
      [5.1.2016] =&gt; 8
      [6.1.2016] =&gt; 0
      [7.1.2016] =&gt; 0
      [8.1.2016] =&gt; 3
  )
  </code></pre>