PHP排序函数实例集绵usort uksort uasort

首先讲下一维数组的排序函数：

常用函数：sort() 按照键值（value）对关联数组进行升序排序；

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

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

ksort() 按照键名（key）对关联数组进行升序排序；

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

按键名排序输出：

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

二维数组排序函数 usort uksort uasort (后面可以跟自定义函数名)

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($arr, 'my_sort'); //自定义函数  usort 根据数值进行排序，但并不会保存关键字
echo "<pre>";
print_r($arr);

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

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

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

)

uksort($arr, 'my_sort');  //排序将基于关键字
echo "<pre>";
print_r($arr);

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

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

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

)

uasort($arr, 'my_sort');  //uasort 关键字就会被保存
echo "<pre>";
print_r($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都是针对一维数组的，并且sort asort根据值升序；

usort uasort uksort 根据二维数组排序，并且usort uasort根据值排序，uasort保留本身键名，uksort根据键名排序