【PHP 每日函数】第 01 周期

摘要：说明将所有键名改为全大写或者小写张三男张三男说明将一个数组分割成多个数组张三男张三男说明返回数组中指定的一列男男女男男女说明将一个数组作键值，另一个数组作值产生一个新的数组说明数组中的键是中的值，数组中的值是的值出现的次数使用键名比

array_change_key_case(array $arr, [, int $case = CASE_LOWER]) : array

说明：将所有键名改为全大写或者小写

$arr = [
    "name" => "张三",
    "Age" => 18,
    "gender" => "男",
];

// case upper
print_r(array_change_key_case($arr, CASE_UPPER));
// output
Array
(
    [NAME] => 张三
    [AGE] => 18
    [GENDER] => 男
)

array_chunk ( array $array , int $size [, bool $preserve_keys = false ] ) : array
说明：将一个数组分割成多个数组

$arr = [
    "name" => "张三",
    "Age" => 18,
    "gender" => "男",
];

print_r(array_chunk($arr, 2));

// output
Array
(
    [0] => Array
        (
            [0] => 张三
            [1] => 18
        )
    [1] => Array
        (
            [0] => 男
        )
)

array_column ( array $input , mixed $column_key [, mixed $index_key = null ] ) : array
说明：返回数组中指定的一列

$arr = [
    0 => [
        "name" => "LeiJian",
        "age" => 18,
        "gender" => "男",
    ],
    1 => [
        "name" => "ZhangSan",
        "age" => 19,
        "gender" => "男",
    ],
    2 => [
        "name" => "LiSi",
        "age" => 20,
        "gender" => "女",
    ],
];

print_r(array_column($arr, NULL, "name"));

// output
Array
(
    [LeiJian] => Array
        (
            [name] => LeiJian
            [age] => 18
            [gender] => 男
        )
    [ZhangSan] => Array
        (
            [name] => ZhangSan
            [age] => 19
            [gender] => 男
        )
    [LiSi] => Array
        (
            [name] => LiSi
            [age] => 20
            [gender] => 女
        )
)

array_combine ( array $keys , array $values ) : array
说明：将一个数组作键值，另一个数组作值产生一个新的数组

$a = [1, 2, 3];

$b = ["a", "b", "c"];

print_r(array_combine($a, $b));

// output
Array
(
    [1] => a
    [2] => b
    [3] => c
)

array_count_values ( array $array ) : array
说明：数组中的键是 array 中的值，数组中的值是 array 的值出现的次数

$arr = [1, "hello", 1, "world", "world"];

print_r(array_count_values($arr));

// output
Array
(
    [1] => 2
    [hello] => 1
    [world] => 2
)

array_diff_key ( array $array1 , array $array2 [, array $... ] ) : array
使用键名（key）比较数组的差集

$arr1 = ["first" => 2, "third" => 3, "fourth" => 4];

$arr2 = ["first" => 1, "second" => 2, "third" => 3];

print_r(array_diff_key($arr1, $arr2));

// output
Array
(
    [fourth] => 4
)

array_diff_uassoc ( array $array1 , array $array2 [, array $... ], callable $key_compare_func ) : array
说明：使用回调函数做索引检查数组差集

$arr1 = ["first" => 2, "third" => 3, "fourth" => 4];

$arr2 = ["first" => 1, "second" => 2, "third" => 3];

print_r(array_diff_uassoc($arr1, $arr2, function($a, $b){

    if ($a === $b) {
        return 0;
    }
    
    return ($a > $b) ? 1 : -1;
}));

// output
Array
(
    [first] => 2
    [fourth] => 4
)

`array_diff ( array $array1 , array $array2 [, array $... ] ) : array
`
说明：比较数组间的差集（array1 比较数组，array2 被比较）

$arr1 = [1, 2, 3, 4, 6];

$arr2 = [2, 3, 4, 5];

print_r(array_diff($arr1, $arr2));

// output
Array
(
    [0] => 1
    [4] => 6
)

array_fill_keys ( array $keys , mixed $value ) : array
说明：使用指定键值（数组）和值进行填充数组

$arr1 = [1, 2, 3, 4, 6];

print_r(array_fill_keys($arr1, "HaHaHa~"));

// output
Array
(
    [1] => HaHaHa~
    [2] => HaHaHa~
    [3] => HaHaHa~
    [4] => HaHaHa~
    [6] => HaHaHa~
)

`array_fill ( int $start_index , int $num , mixed $value ) : array
`
说明：用给定的值进行填充数组，start_index索引开始位置，若为负值，则从 0 开始，num 为填充数量

print_r(array_fill(2, 3, "HaHaHa~"));

// output
Array
(
    [2] => HaHaHa~
    [3] => HaHaHa~
    [4] => HaHaHa~
)

array_filter ( array $array [, callable $callback [, int $flag = 0 ]] ) : array
说明：用回调函数过滤数组中的值（flag 决定 callback接收的参数）

$arr1 = [1, 2, 3, 4, 6];

print_r(array_filter($arr1, function($value){
    if ($value > 2) {
        return $value;
    }
}));

// output
Array
(
    [2] => 3
    [3] => 4
    [4] => 6
)