title: Merge two arrays and insert blank spots where there isn't a match
body: <p>i'm building a request for dates and i need to build an array but keep it in the format of a five day week, so i can easily output it into a table.</p>
  
  <p>i have this array of the current weekdays, monday to friday, that looks like this</p>
  
  <pre><code>$weekDays( [0] =&gt; 2016-12-19 [1] =&gt; 2016-12-20 [2] =&gt; 2016-12-21 [3] =&gt; 2016-12-22 [4] =&gt; 2016-12-23 ) 
  </code></pre>
  
  <p>and an array from a user, which has his personalized dates in it</p>
  
  <pre><code>$user( [0] =&gt; 2016-12-20 [1] =&gt; 2016-12-21 [2] =&gt; 2016-12-22)
  </code></pre>
  
  <p>as you can see, it's only three of the five dates this week. i need to merge these two arrays where the dates match but keep the five day format, like so</p>
  
  <pre><code>$userThisWeek([0] =&gt; NULL [1] =&gt; 2016-12-20 [2] =&gt; 2016-12-21 [3] =&gt; 2016-12-22 [4] =&gt; NULL)
  </code></pre>
  
  <p>how can i go about doing this?</p>