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一週有7天：Sunday、Monday、Tuesday、Wednesday、Thursday、Friday、Saturday、
foreach 用法:Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday,

print_r（weekArray）

Array
(
    [0] => Sunday
    [1] => Monday
    [2] => Tuesday
    [3] => Wednesday
    [4] => Thursday
    [5] => Friday
    [6] => Saturday
)

var_dump（weekArray）

array(7) { [0]=> string(6) "Sunday" [1]=> string(6) "Monday" [2]=> string(7) "Tuesday" [3]=> string(9) "Wednesday" [4]=> string(8) "Thursday" [5]=> string(6) "Friday" [6]=> string(8) "Saturday" }

mealArray=7, 總和=49

sort 排序結果

Array
(
    [0] => Array
        (
            [0] => Friday
            [1] => 星期五
            [2] => 芭樂
            [3] => 7
        )

    [1] => Array
        (
            [0] => Monday
            [1] => 星期一
            [2] => 蘋果
            [3] => 3
        )

    [2] => Array
        (
            [0] => Saturday
            [1] => 星期六
            [2] => 番茄
            [3] => 10
        )

    [3] => Array
        (
            [0] => Sunday
            [1] => 星期日
            [2] => 香蕉
            [3] => 7
        )

    [4] => Array
        (
            [0] => Thursday
            [1] => 星期四
            [2] => 梨
            [3] => 15
        )

    [5] => Array
        (
            [0] => Tuesday
            [1] => 星期二
            [2] => 鳳梨
            [3] => 2
        )

    [6] => Array
        (
            [0] => Wednesday
            [1] => 星期三
            [2] => 檸檬
            [3] => 5
        )

)

var_dump（sort後）

array(7) { [0]=> array(4) { [0]=> string(6) "Friday" [1]=> string(9) "星期五" [2]=> string(6) "芭樂" [3]=> int(7) } [1]=> array(4) { [0]=> string(6) "Monday" [1]=> string(9) "星期一" [2]=> string(6) "蘋果" [3]=> int(3) } [2]=> array(4) { [0]=> string(8) "Saturday" [1]=> string(9) "星期六" [2]=> string(6) "番茄" [3]=> int(10) } [3]=> array(4) { [0]=> string(6) "Sunday" [1]=> string(9) "星期日" [2]=> string(6) "香蕉" [3]=> int(7) } [4]=> array(4) { [0]=> string(8) "Thursday" [1]=> string(9) "星期四" [2]=> string(3) "梨" [3]=> int(15) } [5]=> array(4) { [0]=> string(7) "Tuesday" [1]=> string(9) "星期二" [2]=> string(6) "鳳梨" [3]=> int(2) } [6]=> array(4) { [0]=> string(9) "Wednesday" [1]=> string(9) "星期三" [2]=> string(6) "檸檬" [3]=> int(5) } }
usort 排序結果（小→大）
0Tuesday星期二鳳梨2
1Monday星期一蘋果3
2Wednesday星期三檸檬5
3Friday星期五芭樂7
4Sunday星期日香蕉7
5Saturday星期六番茄10
6Thursday星期四梨15

排序前 mealArray2

Array
(
    [1] => Array
        (
            [Eng] => Monday
            [Cht] => 星期一
            [Fruit] => 蘋果
            [price] => 3
        )

    [2] => Array
        (
            [Eng] => Tuesday
            [Cht] => 星期二
            [Fruit] => 鳳梨
            [price] => 2
        )

    [3] => Array
        (
            [Eng] => Wednesday
            [Cht] => 星期三
            [Fruit] => 檸檬
            [price] => 5
        )

    [4] => Array
        (
            [Eng] => Thursday
            [Cht] => 星期四
            [Fruit] => 梨
            [price] => 15
        )

    [5] => Array
        (
            [Eng] => Friday
            [Cht] => 星期五
            [Fruit] => 芭樂
            [price] => 7
        )

    [6] => Array
        (
            [Eng] => Saturday
            [Cht] => 星期六
            [Fruit] => 番茄
            [price] => 10
        )

    [7] => Array
        (
            [Eng] => Sunday
            [Cht] => 星期日
            [Fruit] => 香蕉
            [price] => 7
        )

)

var_dump（排序前）

array(7) { [1]=> array(4) { ["Eng"]=> string(6) "Monday" ["Cht"]=> string(9) "星期一" ["Fruit"]=> string(6) "蘋果" ["price"]=> int(3) } [2]=> array(4) { ["Eng"]=> string(7) "Tuesday" ["Cht"]=> string(9) "星期二" ["Fruit"]=> string(6) "鳳梨" ["price"]=> int(2) } [3]=> array(4) { ["Eng"]=> string(9) "Wednesday" ["Cht"]=> string(9) "星期三" ["Fruit"]=> string(6) "檸檬" ["price"]=> int(5) } [4]=> array(4) { ["Eng"]=> string(8) "Thursday" ["Cht"]=> string(9) "星期四" ["Fruit"]=> string(3) "梨" ["price"]=> int(15) } [5]=> array(4) { ["Eng"]=> string(6) "Friday" ["Cht"]=> string(9) "星期五" ["Fruit"]=> string(6) "芭樂" ["price"]=> int(7) } [6]=> array(4) { ["Eng"]=> string(8) "Saturday" ["Cht"]=> string(9) "星期六" ["Fruit"]=> string(6) "番茄" ["price"]=> int(10) } [7]=> array(4) { ["Eng"]=> string(6) "Sunday" ["Cht"]=> string(9) "星期日" ["Fruit"]=> string(6) "香蕉" ["price"]=> int(7) } }

排序後 mealArray2（大→小）

Array
(
    [0] => Array
        (
            [Eng] => Thursday
            [Cht] => 星期四
            [Fruit] => 梨
            [price] => 15
        )

    [1] => Array
        (
            [Eng] => Saturday
            [Cht] => 星期六
            [Fruit] => 番茄
            [price] => 10
        )

    [2] => Array
        (
            [Eng] => Friday
            [Cht] => 星期五
            [Fruit] => 芭樂
            [price] => 7
        )

    [3] => Array
        (
            [Eng] => Sunday
            [Cht] => 星期日
            [Fruit] => 香蕉
            [price] => 7
        )

    [4] => Array
        (
            [Eng] => Wednesday
            [Cht] => 星期三
            [Fruit] => 檸檬
            [price] => 5
        )

    [5] => Array
        (
            [Eng] => Monday
            [Cht] => 星期一
            [Fruit] => 蘋果
            [price] => 3
        )

    [6] => Array
        (
            [Eng] => Tuesday
            [Cht] => 星期二
            [Fruit] => 鳳梨
            [price] => 2
        )

)

var_dump（排序後）

array(7) { [0]=> array(4) { ["Eng"]=> string(8) "Thursday" ["Cht"]=> string(9) "星期四" ["Fruit"]=> string(3) "梨" ["price"]=> int(15) } [1]=> array(4) { ["Eng"]=> string(8) "Saturday" ["Cht"]=> string(9) "星期六" ["Fruit"]=> string(6) "番茄" ["price"]=> int(10) } [2]=> array(4) { ["Eng"]=> string(6) "Friday" ["Cht"]=> string(9) "星期五" ["Fruit"]=> string(6) "芭樂" ["price"]=> int(7) } [3]=> array(4) { ["Eng"]=> string(6) "Sunday" ["Cht"]=> string(9) "星期日" ["Fruit"]=> string(6) "香蕉" ["price"]=> int(7) } [4]=> array(4) { ["Eng"]=> string(9) "Wednesday" ["Cht"]=> string(9) "星期三" ["Fruit"]=> string(6) "檸檬" ["price"]=> int(5) } [5]=> array(4) { ["Eng"]=> string(6) "Monday" ["Cht"]=> string(9) "星期一" ["Fruit"]=> string(6) "蘋果" ["price"]=> int(3) } [6]=> array(4) { ["Eng"]=> string(7) "Tuesday" ["Cht"]=> string(9) "星期二" ["Fruit"]=> string(6) "鳳梨" ["price"]=> int(2) } }