摘要：說明將所有鍵名改為全大寫或者小寫張三男張三男說明將一個數組分割成多個數組張三男張三男說明返回數組中指定的一列男男女男男女說明將一個數組作鍵值，另一個數組作值產生一個新的數組說明數組中的鍵是中的值，數組中的值是的值出現的次數使用鍵名比

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

說明：將所有鍵名改為全大寫或者小寫

$arr = [
    "name" => "張三",
    "Age" => 18,
    "gender" => "男",
];

// case upper
print_r(array_change_key_case($arr, CASE_UPPER));
// output
Array
(
    [NAME] => 張三
    [AGE] => 18
    [GENDER] => 男
)

array_chunk ( array $array , int $size [, bool $preserve_keys = false ] ) : array
說明：將一個數組分割成多個數組

$arr = [
    "name" => "張三",
    "Age" => 18,
    "gender" => "男",
];

print_r(array_chunk($arr, 2));

// output
Array
(
    [0] => Array
        (
            [0] => 張三
            [1] => 18
        )
    [1] => Array
        (
            [0] => 男
        )
)

array_column ( array $input , mixed $column_key [, mixed $index_key = null ] ) : array
說明：返回數組中指定的一列

$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
說明：將一個數組作鍵值，另一個數組作值產生一個新的數組

$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
說明：數組中的鍵是 array 中的值，數組中的值是 array 的值出現的次數

$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
使用鍵名（key）比較數組的差集

$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
說明：使用回調函數做索引檢查數組差集

$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
`
說明：比較數組間的差集（array1 比較數組，array2 被比較）

$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
說明：使用指定鍵值（數組）和值進行填充數組

$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
`
說明：用給定的值進行填充數組，start_index索引開始位置，若為負值，則從 0 開始，num 為填充數量

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
說明：用回調函數過濾數組中的值（flag 決定 callback接收的參數）

$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
)