PHP排序函數實例集綿usort uksort uasort

首先講下一維數組的排序函數：
常用函數：sort() 按照鍵值（value）對關聯數組進行升序排序；

$arr=["a"=>4,"b"=>2,"c"=>8,"d"=>"6"];
sort($arr);
echo "<pre>";print_r($arr);

Array
(
    [0] => 2
    [1] => 4
    [2] => 6
    [3] => 8
)   

ksort() 按照鍵名（key）對關聯數組進行升序排序；

$arr=["a"=>4,"b"=>2,"c"=>8,"d"=>"6"];
ksort($arr);
echo "<pre>";
print_r($arr);

按鍵名排序輸出：

Array
(
    [a] => 4
    [b] => 2
    [c] => 8
    [d] => 6
)

二維數組排序函數 usort uksort uasort (後面可以跟自定義函數名)

function my_sort($a,$b)
{  //返回 0 -1 1
if ($a['key1']==$b['key1']) return 0;
return ($a['key1']<$b['key1'])?-1:1; 
}

$arr = [
    ['key1' => 10, 'key2' => 'linux'],
    ['key1' => 20, 'key2' => 'mysql'],
    ['key1' => 9, 'key2' => 'php']
];

usort($arr, 'my_sort'); //自定義函數  usort 根據數值進行排序，但並不會保存關鍵字
echo "<pre>";
print_r($arr);

Array
(
    [0] => Array
        (
            [key1] => 9
            [key2] => php
        )

    [1] => Array
        (
            [key1] => 10
            [key2] => linux
        )

    [2] => Array
        (
            [key1] => 20
            [key2] => mysql
        )

)

uksort($arr, 'my_sort');  //排序將基於關鍵字
echo "<pre>";
print_r($arr);

Array
(
    [2] => Array
        (
            [key1] => 9
            [key2] => php
        )

    [1] => Array
        (
            [key1] => 20
            [key2] => mysql
        )

    [0] => Array
        (
            [key1] => 10
            [key2] => linux
        )

)


uasort($arr, 'my_sort');  //uasort 關鍵字就會被保存
echo "<pre>";
print_r($arr);

Array
(
    [2] => Array
        (
            [key1] => 9
            [key2] => php
        )

    [0] => Array
        (
            [key1] => 10
            [key2] => linux
        )

    [1] => Array
        (
            [key1] => 20
            [key2] => mysql
        )

)

由以上例子可以看出 sort asort ksort都是針對一維數組的，並且sort asort根據值升序；
usort uasort uksort 根據二維數組排序，並且usort uasort根據值排序，uasort保留本身鍵名，uksort根據鍵名排序