如果需要短代码，请使用此函数

BCDIV（）

$size = 11485760;
echo bcdiv($size, 1048576, 0); // return: 10

echo bcdiv($size, 1048576, 2); // return: 10,9

echo bcdiv($size, 1048576, 2); // return: 10,95

echo bcdiv($size, 1048576, 3); // return: 10,953

function formatBytes($bytes, $precision = 2) { 
    $units = array('B', 'KB', 'MB', 'GB', 'TB'); 

    $bytes = max($bytes, 0); 
    $pow = floor(($bytes ? log($bytes) : 0) / log(1024)); 
    $pow = min($pow, count($units) - 1); 

    // Uncomment one of the following alternatives
    // $bytes /= pow(1024, $pow);
    // $bytes /= (1 << (10 * $pow)); 

    return round($bytes, $precision) . ' ' . $units[$pow]; 
} 

(摘自php.net，有很多其他的例子，但我最喜欢这个:-)

根据Leo的回答，添加

对否定的支持 支持0 < value < 1(例如:0.2，会导致log(value) =负数)

如果你想要最大单位Mega，更改$units =爆炸(' '，' K M');

function formatUnit($value, $precision = 2) {
    $units = explode(' ', ' K M G T P E Z Y');

    if ($value < 0) {
        return '-' . formatUnit(abs($value));
    }

    if ($value < 1) {
        return $value . $units[0];
    }

    $power = min(
        floor(log($value, 1024)),
        count($units) - 1
    );

    return round($value / pow(1024, $power), $precision) . $units[$power];
}

灵活的解决方案:

function size($size, array $options=null) {

    $o = [
        'binary' => false,
        'decimalPlaces' => 2,
        'decimalSeparator' => '.',
        'thausandsSeparator' => '',
        'maxThreshold' => false, // or thresholds key
        'suffix' => [
            'thresholds' => ['', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'],
            'decimal' => ' {threshold}B',
            'binary' => ' {threshold}iB',
            'bytes' => ' B'
        ]
    ];

    if ($options !== null)
        $o = array_replace_recursive($o, $options);

    $base = $o['binary'] ? 1024 : 1000;
    $exp = $size ? floor(log($size) / log($base)) : 0;

    if (($o['maxThreshold'] !== false) &&
        ($o['maxThreshold'] < $exp)
    )
        $exp = $o['maxThreshold'];

    return !$exp
        ? (round($size) . $o['suffix']['bytes'])
        : (
            number_format(
                $size / pow($base, $exp),
                $o['decimalPlaces'],
                $o['decimalSeparator'],
                $o['thausandsSeparator']
            ) .
            str_replace(
                '{threshold}',
                $o['suffix']['thresholds'][$exp],
                $o['suffix'][$o['binary'] ? 'binary' : 'decimal']
            )
        );
}

var_dump(size(disk_free_space('/')));
// string(8) "14.63 GB"
var_dump(size(disk_free_space('/'), ['binary' => true]));
// string(9) "13.63 GiB"
var_dump(size(disk_free_space('/'), ['maxThreshold' => 2]));
// string(11) "14631.90 MB"
var_dump(size(disk_free_space('/'), ['binary' => true, 'maxThreshold' => 2]));
// string(12) "13954.07 MiB"

下面是一个使用log10的选项:

<?php

function format_number(float $d): string {
   $e = (int)(log10($d) / 3);
   return sprintf('%.3f', $d / 1e3 ** $e) . ['', ' k', ' M', ' G'][$e];
}

$s = format_number(9012345678);
var_dump($s == '9.012 G');

https://php.net/function.log10

function changeType($size, $type, $end){
    $arr = ['B', 'KB', 'MB', 'GB', 'TB'];
    $tSayi = array_search($type, $arr);
    $eSayi = array_search($end, $arr);
    $pow = $eSayi - $tSayi;
    return $size * pow(1024 * $pow) . ' ' . $end;
}

echo changeType(500, 'B', 'KB');