PHP切割整数工具，类似微信红包金额分配

 Composer地址：https://packagist.org/packages/werbenhu/php-number-slicing

GitHub地址：https://github.com/werbenhu/php-number-slicing

主要代码：NumberSlicing.php

思路：将数字按精度放大倍数，比如切割数字1，切割的份数是10，精度是0.01，则将1放大100 X 10倍，然后再来对加了1000倍权重后的值进行切割。切割完成之后，再将权重去除，保证总值是1。

<?php
namespace Werben\Tools;
use Exception;
class NumberSlicing {
    /**
     * 精确小数点，舍弃最后一位之后的数据（非四舍五入）
     * floor with precision
     * @param $number 要精确的数
     * @param $precision 精度，比如保留到0.01，则该值为2
     * @return float|int
     */
    public static function floorWithPrecision($number, $precision) {
        $power = pow(10, $precision);
        $ret = floor($number * $power) * 1.0 / $power ;
        return $ret;
    }
    /**
     * 精确小数点，按四舍五入保留最后一位
     * round with precision
     * @param $number 要精确的数
     * @param $precision 精度，比如保留到0.01，则该值为2
     * @return float|int
     */
    public static function roundWithPrecision($number, $precision) {
        $power = pow(10, $precision);
        $ret = round($number * $power) * 1.0 / $power ;
        return $ret;
    }
    /**
     * 将数把权重放大，比如1，要按精度0.0001分配，则先将1乘以10000然后再来分配
     * random the sum weights   加上权重之后，整个要切割的数的权重总值
     * @param $weight_items 用来保留，随机分配的权重值
     * @param $count    要切割的份数
     * @param int $each_weight 加上权重之后，每一份平均的权重值
     * @param int $min_weight   加上权重之后，最小额度的值
     * @return float|int
     */
    public static function weightSlicing(&$weight_items, $count, $each_weight = 10, $min_weight = 3)
    {
        $already_count = count($weight_items);
        $cur_random_full_total = ($already_count + 1) * $each_weight;
        $already_random_real_total = 0;
        foreach ($weight_items as $value) {
            $already_random_real_total += $value;
        }
        $cur_random_rest = $cur_random_full_total - $already_random_real_total;
        if ($already_count == $count - 1) {
            $cur_random_rate = $cur_random_rest;
        } else {
            $cur_random_rate_max = $cur_random_rest + $each_weight - $min_weight * 2;
            $cur_random_rate = $min_weight + mt_rand(0, $cur_random_rate_max);
        }
        $weight_items[] = $cur_random_rate;
        return $cur_random_rate;
    }
    /**
     * slicing the number
     * @param int $number
     * @param int $size
     * @param float $precision
     * @param float $min
     * @return array
     * @throws Exception
     */
    public static function numberSlicing($number, $size, $precision = 0.01, $min = 0.01) {
        if ($number * 1.0 / $size <= $min) {
            throw new Exception('min number is bigger than the average value!');
        }
        if ($precision > 1) {
            throw new Exception('precision can\'t bigger than 1!');
        }
        if ($min < $precision) {
            throw new Exception('precision can\'t bigger than min!');
        }
        $weight_items = [];
        $items = [];
        //不加权重情况下，每一份的平均值
        $each_weight = intval($number / $size);
        if ($precision < 1) {
            //如果精度是小数
            if ($each_weight > 1) {
                //如果平均值大于1，则最小额度则直接用min就可以了
                //每一份的平均值乘以权重的值，比如精度为0.01，则每一份的平均值要乘以权重（100）
                $each_weight = intval((1 / $precision) * $number / $size);
                //最小数值也要乘以权重
                $min_weight = intval(1 / $precision) * $min;
            } else {
                //如果平均值小于1，需要将平均值也乘以权重
                $each_weight = intval(1 / $precision);
                $min_weight = $each_weight * $size * $min / $number;
            }
            $precision_num = log10(1 / $precision);
        } else {
            //如果精度是整数(1)
            $min_weight = $min;
            $precision_num = 0;
        }
        $sum_item_number = 0.0;
        $sum_weight = 0.0;
        //先将整个数，随机按最小额度分配
        for ($i = 0; $i < $size; $i++) {
            $cur_weight = self::weightSlicing($weight_items, $size, $each_weight, $min_weight);
            //将权重去除，换算回原先的比例
            $rate = ($number * $cur_weight * 1.00) / ($size * $each_weight);
            $rate = self::floorWithPrecision($rate, $precision_num);
            $sum_item_number += $rate;
            $sum_weight += $cur_weight;
            $items[] = $rate;
        }
        //由于误差，随机分配后，还会遗留一些数没有完全分配完，则将剩下的数随机分配
        if ($precision_num != 0) {
            //如果是切割成小数
            $rest = $number - $sum_item_number;
            while ($rest - 0.00 > PHP_FLOAT_MIN) {
                if ($rest / $min >= 1.0) {
                    //剩余的数大于min最小额度，则将每份最小额度随机分配
                    $random_index = mt_rand(0, $size - 1);
                    $items[$random_index] = self::roundWithPrecision($items[$random_index] + $min, $precision_num);
                    $sum_item_number = self::roundWithPrecision($sum_item_number + $min, $precision_num);
                    $rest = self::roundWithPrecision($number - $sum_item_number, $precision_num);
                } else {
                    //剩余的数小于min最小额度，则将这最后的未分配的数随机分配
                    $random_index = mt_rand(0, $size - 1);
                    $items[$random_index] = self::roundWithPrecision($items[$random_index] + $number - $sum_item_number, $precision_num);
                    $sum_item_number = $number;
                    $rest = $number - $sum_item_number;
                }
            }
        } else {
            //如果是切割成整数
            $rest = $number - $sum_item_number;
            while ($rest > 0) {
                if ($rest / $min >= 1) {
                    $random_index = mt_rand(0, $size - 1);
                    $items[$random_index] += $min;
                    $sum_item_number += $min;
                    $rest = $number - $sum_item_number;
                } else {
                    $random_index = mt_rand(0, $size - 1);
                    $items[$random_index] += $rest;
                    $sum_item_number += $rest;
                    $rest = $number - $sum_item_number;
                }
            }
        }
        return $items;
    }
}

　　测试代码：

use Werben\Tools\NumberSlicing;

function testIntSlicing2IntOne() {
    $precision = 1; //精确度 eg: 1, 0.1, 0.01, 0.01
    $size = 10;         //切割的份数，the size of the number to slicing
    $min = 3;        //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
    $number = 100;      //要切割的数字，the number
    $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);

    $sum = 0.0;
    $ret_min = $number;
    foreach ($items as $value) {
        $sum += $value;
        if ($ret_min > $value) {
            $ret_min = $value;
        }
    }
    $count = count($items);
    echo "count: $count, sum: $sum, ret_min: $ret_min\n";
    echo "items : ". json_encode($items) ."\n";
}

function testIntSlicing2IntTwo() {
    $precision = 1; //精确度 eg: 1, 0.1, 0.01, 0.01
    $size = 30;         //切割的份数，the size of the number to slicing
    $min = 18666;        //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
    $number = 800000;      //要切割的数字，the number
    $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);

    $sum = 0.0;
    $ret_min = $number;
    foreach ($items as $value) {
        $sum += $value;
        if ($ret_min > $value) {
            $ret_min = $value;
        }
    }
    $count = count($items);
    echo "count: $count, sum: $sum, ret_min: $ret_min\n";
    echo "items : ". json_encode($items) ."\n";
}

function testIntSlicing2FloatOne() {
    $precision = 0.01; //精确度 eg: 1, 0.1, 0.01, 0.01
    $size = 1000;         //切割的份数，the size of the number to slicing
    $min = 0.05;        //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
    $number = 100;      //要切割的数字，the number
    $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);

    $sum = 0.0;
    $ret_min = $number;
    foreach ($items as $key => $value) {
        $sum += $value;
        if ($ret_min > $value) {
            $ret_min = $value;
        }
    }
    $count = count($items);
    echo "count: $count, sum: $sum, ret_min: $ret_min\n";
    echo "items: ". json_encode($items) ."\n";
}

function testIntSlicing2FloatTwo() {
    $precision = 0.00001; //精确度 eg: 1, 0.1, 0.01, 0.01
    $size = 1000;         //切割的份数，the size of the number to slicing
    $min = 0.00005;        //最小额度，最小额度必须大于最小精度，min amount eg: 3, 0.23, 0.05, 0.008
    $number = 5;      //要切割的数字，the number
    $items = NumberSlicing::numberSlicing($number, $size, $precision, $min);

    $sum = 0.0;
    $ret_min = $number;
    foreach ($items as $key => $value) {
        $sum += $value;
        if ($ret_min > $value) {
            $ret_min = $value;
        }
    }
    $count = count($items);
    echo "count: $count, sum: $sum, ret_min: $ret_min\n";
    echo "items: ". json_encode($items) ."\n";
}