title: php return only duplicated entries from an array
body: <p>I want to retrieve all duplicated entries from a array. Is this possible in PHP?</p>
  
  <pre><code>array(
      1 =&gt; '1233',
      2 =&gt; '12334',
      3 =&gt; 'Hello',
      4 =&gt; 'hello',
      5 =&gt; 'U'
  );
  </code></pre>
  
  <p>I want to return an array with just the duplicate value: “hello”.</p>
  
  <p>Desired output array:</p>
  
  <pre><code>array(
      1 =&gt; 'Hello',
      2 =&gt; 'hello'
  );
  </code></pre>