php常用内置函数-Array

array_chunk - 将一个数组分割成多个

• array_chunk(array $array, int $length, bool $preserve_keys = false): array

    $arr = [1, 2, 3, 'h', 5=>'w'];
    //第三个参数设为true则保留原数组的键名
    print_r(array_chunk($arr, 3, true));
        //结果
        Array
        (
            [0] => Array
                (
                    [0] => 1
                    [1] => 2
                    [2] => 3
                )
            [1] => Array
                (
                    [3] => h
                    [5] => w
                )
        )

array_column - 返回数组中指定列的值

• array_column(array $array, int|string|null $column_key, int|string|null $index_key = null): array

    $arr = [
                [
                    'id' => 1,
                    'age' => 13,
                    'name' => 'alex'
                ],
                [
                    'id' => 12,
                    'age' => 23,
                    'name' => 'bianca'
                ],
            ];
                //结果
                Array
                (
                    [0] => alex
                    [1] => bianca
                )

array_count_values - 统计数组中所有的值

• array_count_values(array $array): array

    $arr = [1, 2, 3, 2, 1, 'age', 'name', 'age'];
    print_r(array_count_values($arr));
        //结果
        Array
        (
            [1] => 2
            [2] => 2
            [3] => 1
            [age] => 2
            [name] => 1
        )

array_diff - 计算数组的差集

• array_diff(array $array, array …$arrays): array

    $arr1 = [1, 2, 3];
    $arr2 = [1, 3, 4];
  
    print_r(array_diff($arr1, $arr2));
        //结果
        Array
        (
            [1] => 2
        )

array_intersect - 计算数组的交集

• array_intersect(array $array, array …$arrays): array

    $arr1 = ['a' => 3, 5, 7, 9];
    $arr2 = ['b' => 3, 5];
    print_r(array_intersect($arr1, $arr2));
        Array
        (
            [a] => 3
            [0] => 5
        )

array_filter - 使用回调函数过滤数组中的元素

• array_filter(array $array, ?callable $callback = null, int $mode = 0): array

    $arr = [1, 2, 3, 4];
    print_r(array_filter($arr, function($v){return $v % 2 == 0;}));
        //结果
        Array
        (
            [1] => 2
            [3] => 4
        )

array_map - 给数组的每个元素执行回调函数

• array_map(?callable $callback, array $array, array …$arrays): array

    $arr = [1, 2, 3, 4];
    print_r(array_map(function($v){return $v * 2;}, $arr));

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

array_merge - 合并一个或者多个数组

• array_merge(array …$arrays): array

    $arr1 = [1, 2, 3, 4];
    $arr2 = [1, 3,4, 'b'=>7];
  
    print_r(array_merge($arr1, $arr2));
        //结果
        Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
            [4] => 1
            [5] => 3
            [6] => 4
            [b] => 7
        )

array_pop — 弹出数组最后一个单元（出栈）

• array_pop(array &$array): mixed

    $arr = [1, 2, 3];
  
    echo array_pop($arr); //3

array_push — 将一个或多个单元压入数组的末尾（入栈）

• array_push(array &$array, mixed $value1, mixed $… = ?): int

    $arr = [1, 2, 3];
  
    array_push($arr, 4);
    print_r($arr);
        Array
        (
            [0] => 1
            [1] => 2
            [2] => 3
            [3] => 4
        )

array_reduce — 用回调函数迭代地将数组简化为单一的值

• array_reduce(array $array, callable $callback, mixed $initial = null): mixed

   $arr = [1, 2, 3];
  
   echo array_reduce($arr, function($a, $b){return $a + $b;}, 10); //16
   //如果指定了第三个参数，则为回调函数的初始值

array_reverse — 返回单元顺序相反的数组

• array_reverse(array $array, bool $preserve_keys = false): array

   $arr = [1, 2, 3];
  
   print_r(array_reverse($arr));
       Array
       (
           [0] => 3
           [1] => 2
           [2] => 1
       )

array_search — 在数组中搜索给定的值，如果成功则返回首个相应的键名

• array_search(mixed $needle, array $haystack, bool $strict = false): int|string|false

    $arr = [1, 2, 3];
  
    echo array_search(2, $arr); //1

array_unique — 移除数组中重复的值

• array_unique(array $array, int $flags = SORT_STRING): array

    $arr = [4, 2, 3, 3, 1];
  
    print_r(array_unique($arr));
        Array
        (
            [0] => 4
            [1] => 2
            [2] => 3
            [4] => 1
        )
    //此时会返回一个新数组，不会修改原数组

array_shift - 移除数组开头的元素

• array_shift(array &$array): mixed

    $arr = [4, 2, 3];
  
    echo array_shift($arr); //4

array_unshift - 在数组开头插入一个或多个单元

• array_unshift(array &$array, mixed …$values): int

    $arr = [4, 2, 3];
  
    array_unshift($arr, [1 ,2]);
    print_r($arr);
        Array
        (
            [0] => Array
                (
                    [0] => 1
                    [1] => 2
                )
  
            [1] => 4
            [2] => 2
            [3] => 3
        )

array_walk — 使用用户自定义函数对数组中的每个元素做回调处理

• array_walk(array|object &$array, callable $callback, mixed $arg = null): bool

    $arr = [4, 2, 3];
  
    array_walk($arr, function($v, $k){echo $k . '===' . $v;}); //0===41===22===3

in_array — 检查数组中是否存在某个值

• in_array(mixed $needle, array $haystack, bool $strict = false): bool

    $arr = [4, 2, 3];
  
    echo in_array(3, $arr); //1

compact — 建立一个数组，包括变量名和它们的值

• compact(array|string $var_name, array|string …$var_names): array

    $str = 'php';
    $arr = [];
    print_r(compact('str', $arr));
        Array
        (
            [str] => php
        )

count — 统计数组、Countable 对象中所有元素的数量

• count(Countable|array $value, int $mode = COUNT_NORMAL): int

    $arr = [1, 2, 3];
    echo count($arr); //3

krsort — 对数组按照键名逆向排序

• krsort(array &$array, int $flags = SORT_REGULAR): bool

    $arr = ['d' => 1, 'c' => 2, 'e' => 3];
    krsort($arr);
    print_r($arr);
        Array
        (
            [e] => 3
            [d] => 1
            [c] => 2
        )

list — 把数组中的值赋给一组变量

• list(mixed $var, mixed …$vars = ?): array

    $info = ['coffee', 'brown', 'caffeine'];
    list($drink, $color, $power) = $info;

range 根据范围创建数组，包含指定的元素

• range(string|int|float $start, string|int|float $end, int|float $step = 1): array

    print_r(range(0, 3));
        Array
        (
            [0] => 0
            [1] => 1
            [2] => 2
            [3] => 3
        )

shuffle — 打乱数组

• shuffle(array &$array): bool

    $arr = [1, 3, 4, 'b'=>7];
  
    shuffle($arr);
    print_r($arr);
        Array
        (
            [0] => 7
            [1] => 1
            [2] => 4
            [3] => 3
        )

sort - 对数组进行升序排序

• sort(array &$array, int $flags = SORT_REGULAR): bool

    $arr = [5, 3, 4, 'b'=>7];
  
    sort($arr);
    print_r($arr);
        Array
        (
            [0] => 3
            [1] => 4
            [2] => 5
            [3] => 7
        )

array_splice 去掉数组中的某一部分并用其它值取代

• 定义

    array_splice(
        array &$array,
        int $offset,
        ?int $length = null,
        mixed $replacement = []
    ): array

    $arr = [1, 2, 3];
  
    array_splice($arr,1 , 0, 'insert');
    print_r($arr);
        Array
        (
            [0] => 1
            [1] => insert
            [2] => 2
            [3] => 3
        )
    //此函数可以向数组的指定位置插入元素

应用

• 找出数组中最大值的下标

    $arr = [3, 5, 7, 9];
    echo array_search(max($arr), $arr); //3

• pathinfo - 返回文件路径的信息

    //pathinfo(string $path, int $flags = PATHINFO_ALL): array|string
    $str = 'index.php';
  
    $file_attrs = pathinfo($str);
    print_r($file_attrs);
        Array
        (
            [dirname] => .
            [basename] => index.php
            [extension] => php
            [filename] => index
        )
    echo $file_attrs['extension']; //php

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