二次元配列のソート。追記：複数項目でのソート

<?php
$array   = array();
$array[] = array('name' => 'リンゴ', 'price' => '100',  'order' => 4);
$array[] = array('name' => 'ミカン', 'price' => '60',   'order' => 3);
$array[] = array('name' => 'バナナ', 'price' => '100',  'order' => 2);
$array[] = array('name' => 'メロン', 'price' => '5000', 'order' => 1);
$array[] = array('name' => 'スイカ', 'price' => '100',  'order' => 2);
$array[] = array('name' => 'イチゴ', 'price' => '100',  'order' => 4);


/********** ソート処理 **********/
foreach($array as $_key_ => $_line_)
{
	$_arrayName_[$_key_] = $_line_['price'];
}
array_multisort($_arrayName_, SORT_ASC, $array);
/********* /ソート処理 **********/

ソート前

Array
(
    [a] => Array
        (
            [name] => りんご
            [price] => 100
        )

    [b] => Array
        (
            [name] => みかん
            [price] => 60
        )

    [c] => Array
        (
            [name] => バナナ
            [price] => 300
        )

    [d] => Array
        (
            [name] => メロン
            [price] => 5000
        )

    [e] => Array
        (
            [name] => スイカ
            [price] => 1500
        )
)

ソート後

Array
(
    [b] => Array
        (
            [name] => みかん
            [price] => 60
        )

    [a] => Array
        (
            [name] => りんご
            [price] => 100
        )

    [c] => Array
        (
            [name] => バナナ
            [price] => 300
        )

    [e] => Array
        (
            [name] => スイカ
            [price] => 1500
        )

    [d] => Array
        (
            [name] => メロン
            [price] => 5000
        )
)

キーとの関係を保持しつつ、値段で昇順にソートされています。

複数の項目でソート

$array変数をキーprice、order、nameの順で昇順ソート。
※配列長が2未満の場合はエラーが出るので注意。

<?php
$array   = array();
$array[] = array('name' => 'リンゴ', 'price' => '100',  'order' => 4);
$array[] = array('name' => 'ミカン', 'price' => '60',   'order' => 3);
$array[] = array('name' => 'バナナ', 'price' => '100',  'order' => 2);
$array[] = array('name' => 'メロン', 'price' => '5000', 'order' => 1);
$array[] = array('name' => 'スイカ', 'price' => '100',  'order' => 2);
$array[] = array('name' => 'イチゴ', 'price' => '100',  'order' => 4);


/********** 列方向の配列を得る **********/
foreach($array as $_key_ => $_line_)
{
    $_array_price_[$_key_] = $_line_['price'];
    $_array_order_[$_key_] = $_line_['order'];
    $_array_name_[$_key_]  = $_line_['name'];
}
/********* /列方向の配列を得る **********/


/********** ソート処理 **********/
array_multisort
(
    $_array_price_, SORT_ASC,
    $_array_order_, SORT_ASC,
    $_array_name_,  SORT_ASC,
    $array
);
/********* /ソート処理 **********/