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groupBy

向数组添加分组功能。数组可以通过数组键或回调函数进行分组。

示例 1：按数组键分组

<?php

use function PeteMc\GroupBy\groupBy;

$students = [
    ['name' => 'adam', 'year' => '10'],
    ['name' => 'becky', 'year' => '12'],
    ['name' => 'chris', 'year' => '11'],
    ['name' => 'deborah', 'year' => '10'],
    ['name' => 'edward', 'year' => '12'],
];

$groupedByYear = groupBy($students, 'year');

/*
$groupedByYear is equal to
[
    10 => [
        ['name' => 'adam', 'year' => '10'],
        ['name' => 'deborah', 'year' => '10'],
    ],
    11 => [
        ['name' => 'chris', 'year' => '11'],
    ],
    12 => [
        ['name' => 'becky', 'year' => '12'],
        ['name' => 'edward', 'year' => '12'],
    ],
]
*/

示例 2：按回调函数分组

<?php

use function PeteMc\GroupBy\groupBy;

$numberList = [1, 2, 3, 4, 5, 987, 554, 32];

// The array item value will be passed to the callback.
$oddOrEven = function ($n) {
    return $n % 2 == 0 ? 'even' : 'odd';
};

$oddAndEven = groupBy($numberList, $oddOrEven);

/*
$oddAndEven is now equal to
[
    'odd' => [1, 3, 5, 987],
    'even' => [2, 4, 554, 32],
];
*/

示例 3：按回调函数在对象数组中分组

类似于上面的示例，输入数组可以是一个对象数组。

<?php

use function PeteMc\GroupBy\groupBy;

// $students in an array of `stdClass Object`
$students = [
    (object) ['name' => 'adam', 'year' => '10'],
    (object) ['name' => 'becky', 'year' => '12'],
    (object) ['name' => 'chris', 'year' => '11'],
    (object) ['name' => 'deborah', 'year' => '10'],
    (object) ['name' => 'edward', 'year' => '12'],
];

$groupByYear = function ($student) {
    return $student->year;
};

$groupedByYear = groupBy($students, $groupByYear);

/*
$groupedByYear is now equal to
[
    [10] => [
        [0] => stdClass Object
            (
                [name] => adam
                [year] => 10
            )
        [1] => stdClass Object
            (
                [name] => deborah
                [year] => 10
            )
        ]
    [12] => [
        [0] => stdClass Object
            (
                [name] => becky
                [year] => 12
            )
        [1] => stdClass Object
            (
                [name] => edward
                [year] => 12
            )
        ]
    [11] => [
        [0] => stdClass Object
            (
                [name] => chris
                [year] => 11
            )
    ]
]
*/