title: Restructure array to join elements from 3rd position to end of array and store as 3rd element
body: <p>I have arrays like this:</p>
  
  <pre><code>Array(
      [0] =&gt; 85
      [1] =&gt; 85167920
      [2] =&gt; ELECTRICAL/ELECTRONIC
      [3] =&gt; DEVICES
      [4] =&gt; FOR
      [5] =&gt; REPELLING
      [6] =&gt; INSECTS
      [7] =&gt; (E.G.MOSQUITOES
      [8] =&gt; ETC)
  )
  </code></pre>
  
  <p>and</p>
  
  <pre><code>Array(
     [0] =&gt; 85
     [1] =&gt; 851680
     [2] =&gt; ELECTRIC
     [3] =&gt; HEATING
     [4] =&gt; RESISTORS
  )
  </code></pre>
  
  <p>I want arrays like this:</p>
  
  <pre><code>Array(
      [0] =&gt; 85
      [1] =&gt; 851680
      [2] =&gt; ELECTRIC HEATING RESISTORS
  )
  </code></pre>
  
  <p>and</p>
  
  <pre><code>Array(
      [0] =&gt; 85
      [1] =&gt; 85167920
      [2] =&gt; ELECTRICAL/ELECTRONIC DEVICES FOR REPELLING INSECTS (E.G.MOSQUITOES ETC)
  )
  </code></pre>
  
  <p>I am not sure about what method to use: merge / combine / push.<br>
  What should I use?</p>