//定义一个学生数组
$students = array(
  256=>array('name'=>'jon','grade'=>98.5),
  2=>array('name'=>'vance','grade'=>85.1),
  9=>array('name'=>'stephen','grade'=>94.0),
  364=>array('name'=>'steve','grade'=>85.1),
  68=>array('name'=>'rob','grade'=>74.6),
);
//按照名称进行排序
function name_sort($x, $y)
{
  return strcasecmp($x['name'],$y['name']);
}
//按照成绩进行排序
function grade_sort($x,$y)
{
  return ($x['grade'] > $y['grade']);
}
//应用
uasort($students, name_sort);
uasort($students, grade_sort);