title: PHP get previous array element knowing current array key
body: <p>I have an array with specific keys:</p>
  
  <pre><code>array(
      420 =&gt; array(...), 
      430 =&gt; array(...), 
      555 =&gt; array(...)
  )
  </code></pre>
  
  <p>In my application I know current key (for example <code>555</code>). And I want to get the previous array element. In this example it is array element with key <code>430</code>. How can I do this in PHP? I tried to work with <code>prev()</code>, but for this function we should know current array element. I didn't find function, what set the current array element.</p>