PHP实现根据数组的值进行分组的方法

实现根据数组的值进行分组的方法，可以借助PHP自带的函数array_reduce()和array_merge()。具体步骤如下：

1. 定义初始结果数组

通过array_reduce()函数对数组进行遍历，将结果放入一个初始化的空数组中。

$groups = array_reduce($arr, function($result, $item) {
    ...
    return $result;
}, array());

1. 判断值是否已有分组

在循环中，通过判断当前值是否已经有分组来决定将其添加到已有分组中，还是创建新的分组。

$groups = array_reduce($arr, function($result, $item) {
    $grouped = false;
    foreach ($result as $key => $group) {
        if ($item['group'] == $key) {
            $result[$key][] = $item;
            $grouped = true;
            break;
        }
    }
    if (!$grouped) {
        $result[$item['group']] = array($item);
    }
    return $result;
}, array());

1. 返回分组后的结果

最后，通过返回结果数组$groups来获取分组后的数组数据。

完整代码示例1：

<?php
$arr = array(
    array('name' => 'apple','group' => 'fruit'),
    array('name' => 'pear','group' => 'fruit'),
    array('name' => 'carrot','group' => 'vegetable'),
    array('name' => 'onion','group' => 'vegetable'),
    array('name' => 'beef','group' => 'meat'),
);

$groups = array_reduce($arr, function($result, $item) {
    $grouped = false;
    foreach ($result as $key => $group) {
        if ($item['group'] == $key) {
            $result[$key][] = $item;
            $grouped = true;
            break;
        }
    }
    if (!$grouped) {
        $result[$item['group']] = array($item);
    }
    return $result;
}, array());

print_r($groups);
?>

输出结果：

Array
(
    [fruit] => Array
        (
            [0] => Array
                (
                    [name] => apple
                    [group] => fruit
                )

            [1] => Array
                (
                    [name] => pear
                    [group] => fruit
                )

        )

    [vegetable] => Array
        (
            [0] => Array
                (
                    [name] => carrot
                    [group] => vegetable
                )

            [1] => Array
                (
                    [name] => onion
                    [group] => vegetable
                )

        )

    [meat] => Array
        (
            [0] => Array
                (
                    [name] => beef
                    [group] => meat
                )

        )

)

完整代码示例2：

<?php
$arr = array(
    array('name' => 'John','age' => 25,'gender' => 'male'),
    array('name' => 'Mark','age' => 30,'gender' => 'male'),
    array('name' => 'Jenny','age' => 22,'gender' => 'female'),
    array('name' => 'Amy','age' => 26,'gender' => 'female'),
    array('name' => 'David','age' => 19,'gender' => 'male'),
);

$groups = array_reduce($arr, function($result, $item) {
    $grouped = false;
    foreach ($result as $key => $group) {
        if ($item['gender'] == $key) {
            $result[$key][] = $item;
            $grouped = true;
            break;
        }
    }
    if (!$grouped) {
        $result[$item['gender']] = array($item);
    }
    return $result;
}, array());

print_r($groups);
?>

输出结果：

Array
(
    [male] => Array
        (
            [0] => Array
                (
                    [name] => John
                    [age] => 25
                    [gender] => male
                )

            [1] => Array
                (
                    [name] => Mark
                    [age] => 30
                    [gender] => male
                )

            [2] => Array
                (
                    [name] => David
                    [age] => 19
                    [gender] => male
                )

        )

    [female] => Array
        (
            [0] => Array
                (
                    [name] => Jenny
                    [age] => 22
                    [gender] => female
                )

            [1] => Array
                (
                    [name] => Amy
                    [age] => 26
                    [gender] => female
                )

        )

)