title: function array_multisort in php change the key of my array
body: <p>I have this array: </p>
  
  <pre><code>$array["4E-952778"][0]['fileName'] = "File 1";
  $array["4E-952778"][0]['product'] = "Muse On Demand";
  $array["4E-952778"][1]['fileName'] = "File 2";
  $array["4E-952778"][1]['product'] = "Muse On Demand";   
  
  $array["15210"][0]['fileName'] = "File 3";
  $array["15210"][0]['product'] = "4Manager"; 
  $array["15210"][1]['fileName'] = "File 4";
  $array["15210"][1]['product'] = "4Manager";
  
  $products = array();
  foreach ($array as $key =&gt; $row) {
      $products[$key] = $row[0]['product'];       
  }
  array_multisort($products, SORT_ASC, $array);
  
  print_r($array);
  </code></pre>
  
  <p>and the result is this :</p>
  
  <pre><code>Array
  (
      [0] =&gt; Array
          (
              [0] =&gt; Array
                  (
                      [fileName] =&gt; File 3
                      [product] =&gt; 4Manager
                  )
  
              [1] =&gt; Array
                  (
                      [fileName] =&gt; File 4
                      [product] =&gt; 4Manager
                  )
  
          )
      [4E-952778] =&gt; Array
          (
              [0] =&gt; Array
                  (
                      [fileName] =&gt; File 1
                      [product] =&gt; Muse On Demand
                  )
              [1] =&gt; Array
                  (
                      [fileName] =&gt; File 2
                      [product] =&gt; Muse On Demand
                  )
          )
  )
  </code></pre>
  
  <p>As you can observe the function <code>array_multisort()</code> change the key: <code>15210</code> to <code>0</code> why this change?</p>