$testArr = array(
    'php' => array(
        'author' => 'allen',
        'price' => 40,
    ),
    'java' => array(
        'author' => 'james',
        'price' => 55,
    ),
    'mysql' => array(
        'author' => 'gates',
        'price' => 30,
    ),
    'html' => array(
        'author' => 'bill',
        'price' => 21,
    )
);

uasort($testArr, create_function('$a,$b', 'return $a["price"]>$b["price"];'));//价格升序，降序改成<

------解决方案--------------------
PHP code

<?
    $testArr = array(
        'php' => array(
            'author' => 'allen',
            'price' => 40,
        ),
        'java' => array(
            'author' => 'james',
            'price' => 55,
        ),
        'mysql' => array(
            'author' => 'gates',
            'price' => 30,
        ),
        'html' => array(
            'author' => 'bill',
            'price' => 21,
        )
    );
    function my_sort($a, $b){
      return $a['price'] > $b['price'];
    }
    uasort($testArr, "my_sort");
    print_r($testArr);
?>

------解决方案--------------------

PHP code
foreach ($testArr as $v) {
    $k[] = $v['price'];
}
array_multisort($k, SORT_DESC,$testArr);
print_r(array_slice($testArr,0,3));

------解决方案--------------------
楼上几位共使用了两种类型的三种方法
对比如下
PHP code
$testArr = array(
    'php' => array(
        'author' => 'allen',
        'price' => 40,
    ),
    'java' => array(
        'author' => 'james',
        'price' => 55,
    ),
    'mysql' => array(
        'author' => 'gates',
        'price' => 30,
    ),
    'html' => array(
        'author' => 'bill',
        'price' => 21,
    )
);

/*** 应用回调函数 ***/
function func1($ar) {
  uasort($ar, create_function('$a,$b', 'return $a["price"]>$b["price"];'));//价格升序，降序改成<
}

/*** 不使用回调函数 ***/
function func2($ar) {
  foreach ($ar as $key => $row) {
    $price[$key] = $row['price'];
  }
  array_multisort($price, SORT_ASC,$ar);
}

/*** 应用 php5.3 闭包 ***/
function func3($ar) {
  array_multisort(array_map(function($v){return $v['price'];},$ar),$ar);
}
check_speed(200, 'func2', $testArr);
check_speed(200, 'func3', $testArr);
check_speed(200, 'func1', $testArr);