Here is a function to sort an array by the key of his sub-array with keep key in top level.

<?php
function sksort(&$array, $subkey="id", $sort_descending=false, $keep_keys_in_sub = false) {
    $temp_array = $array;

    foreach ($temp_array as $key => &$value) {
      
      $sort = array();
      foreach ($value as $index => $val) {
          $sort[$index] = $val[$subkey];
      }
      
      asort($sort);
      
      $keys = array_keys($sort);
      $newValue = array();
      foreach ($keys as $index) {
        if($keep_keys_in_sub)
            $newValue[$index] = $value[$index];
          else
            $newValue[] = $value[$index];
      }
      
      if($sort_descending)
        $value = array_reverse($newValue, $keep_keys_in_sub);
      else
        $value = $newValue;
    }
    
    $array = $temp_array;
  }
?>