title: Opposite of array_chunk
body: <p><code>array_chunk</code> splits an array into multiple arrays using a chunk size to make the cuts.</p>
  
  <p>What if I have an array of arrays of values, and I just want one big array of values?</p>
  
  <p>I could use <code>array_merge</code>, but that would require me to enumerate all the sub-arrays, of which there may be a variable number.</p>
  
  <p>For now, my solution is:</p>
  
  <pre><code>foreach($input as $tmp) {foreach($tmp as $val) {
      ...
  }}
  </code></pre>
  
  <p>But that's kind of messy and only works because I want to use the values. What if I wanted to store the array somewhere?</p>
  
  <p>EDIT: The input is coming from a set of <code>&lt;select multiple&gt;</code> boxes, used to select items from multiple categories. Each item has a globally unique (among items) ID, so I just want to combine the input into a single array and run through it.</p>
  
  <p>The input might look like:</p>
  
  <pre><code>[[4,39,110],[9,54,854,3312,66950],[3]]
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>[4,39,110,9,54,854,3312,66950,3]
  </code></pre>
  
  <p>or:</p>
  
  <pre><code>[3,4,9,29,54,110,854,3312,66950]
  </code></pre>