title: Get the leaf node values of a multi-dimensional array with an indeterminant depth
body: <p>I have an array like this:</p>
  <pre><code>Array
  (
      [23] =&gt; 540,
      [25] =&gt; Array
          (
              [656] =&gt; Array(671 ,680),
              [345] =&gt; 400
          )
  )
  </code></pre>
  <p>I want to get the values:</p>
  <pre><code>540, 671, 680, 400
  </code></pre>
  <p>The problem for me is, that this array is growing and I don't know how many levels deep it will be.</p>