title: php search array  which contains "key : value" items
body: <p>If i have an array $output that looks like this,  how can i search the array and echo out the duration value which in this case is 30. Duration is not always key [18].  </p>
  
  <pre><code>Array
  (
      [16] =&gt;     hasKeyframes    : true
      [17] =&gt;     hasMetadata     : true
      [18] =&gt;     duration        : 30
      [19] =&gt;     audiosamplerate : 22000
      [20] =&gt;     audiodatarate   : 68
      [21] =&gt;     datasize        : 1103197
  }
  </code></pre>