去除2维数组中key重复的子数组

$aa = array(
  array('id' => 123, 'name' => '张三'),
  array('id' => 123, 'name' => '李四'),
  array('id' => 124, 'name' => '王五'),
  array('id' => 125, 'name' => '赵六'),
  array('id' => 126, 'name' => '赵六')
  );
  $arr = array();
  foreach($aa as $k => $v){
       if(in_array($v['name'], $arr)){ 
         unset($aa[$k]);
      }
    else {
        $arr[] = $v['name'];
      }
    }