Converts int bytes to a highest, rounded, multiplication that is IEC compliant.

bytesToString.php

<?php
/**
 * Converts int bytes to a highest, rounded, multiplication that is IEC compliant.
 * 
 * @link https://en.wikipedia.org/wiki/Binary_prefix
 * 
 * @param int $size       Number of bytes to convert
 * @param int $precision  Rounding precision (defaults to 0)
 * @return string Highest rounded multiplication with IEC suffix
 */
function bytesToString($size, $precision = 0) {
    if ($size > 1125899906842624) {
        $size /= 1125899906842624;
        $suffix = 'PiB';
    } elseif ($size > 1099511627776) {
        $size /= 1099511627776;
        $suffix = 'TiB';
    } elseif ($size > 1073741824) {
        $size /= 1073741824;
        $suffix = 'GiB';
    } elseif ($size > 1048576) {
        $size /= 1048576;
        $suffix = 'MiB';
    } elseif ($size > 1024) {
        $size /= 1024;
        $suffix = 'KiB';
    } else {
        $suffix = 'B';
    }
    
    return round($size, $precision) . ' ' . $suffix;
}