title: PHP Array, get the key based on a value
body: <p>If I have this array</p>
  
  <pre><code>$england = array(
          'AVN' =&gt; 'Avon',
          'BDF' =&gt; 'Bedfordshire',
          'BRK' =&gt; 'Berkshire',
          'BKM' =&gt; 'Buckinghamshire',
          'CAM' =&gt; 'Cambridgeshire',
          'CHS' =&gt; 'Cheshire'
  );
  </code></pre>
  
  <p>I want to be able to get the three letter code from the full text version, how would i write the following function:</p>
  
  <pre><code>$text_input = 'Cambridgeshire';
  function get_area_code($text_input){
      //cross reference array here
      //fish out the KEY, in this case 'CAM'
      return $area_code;
  }
  </code></pre>
  
  <p>thanks!</p>