title: How to convert a multidimensional array to a single dimensional array?
body: <p>I want to turn (in PHP) something like</p>
  
  <pre><code>(["a"] =&gt; (
      ["x"] =&gt; "foo",
      ["y"] =&gt; "bar"),
  ["b"] =&gt; "moo",
  ["c"] =&gt; (
      ["w"] =&gt; (
          ["z"] =&gt; "cow" )
          )
  )
  </code></pre>
  
  <p>into</p>
  
  <pre><code>(["a.x"] =&gt; "foo",
  ["a.y"] =&gt; "bar",
  ["b"] =&gt; "moo",
  ["c.w.z"] =&gt; "cow")
  </code></pre>
  
  <p>How do I achieve that?</p>