title: Issue in Incrementing array values in PHP
body: <p>In my project I increase values of firstArray +3.After I increase values of secondArray  +7 .</p>
  
  <pre><code>   $firstArray = array(
        'a' =&gt; 1,
        'b' =&gt; 3,
        'c' =&gt; 5,
     );
  
  foreach ($firstArray as &amp;$item) {
      $item += 3;
  }
  print_r($firstArray);
  </code></pre>
  
  <p><strong>Result:</strong> <code>Array ( [a] =&gt; 4 [b] =&gt; 6 [c] =&gt; 8)</code></p>
  
  <pre><code>  $secondArray = array(
      'a' =&gt; 11,
      'b' =&gt; 13,
      'c' =&gt; 17,
  );
  
  foreach ($secondArray as $key=&gt;$item) {
      $secondArray[$key] += 7;
  }
  
  print_r($secondArray);
  </code></pre>
  
  <p><strong>Result:</strong> <code>Array ( [a] =&gt; 18 [b] =&gt; 20 [c] =&gt; 24 )</code></p>
  
  <p><strong>But</strong> problem is when I did <code>print_r($firstArray) again;</code> I have this result:
  Array ( [a] => 4 [b] => 6 [c] => 17 ) </p>
  
  <p>Why there is the difference in result fisrt and thisrd?</p>