php8.0 - number to metric with prefix for things like human readable file size

numberToMetric.php

<?php

function numberToMetric(int|float $number, int $significantDigits = 3, bool $binary = false): string {
    static $prefixes = ['y','z','a','f','p','n','μ','m','','k','M','G','T','P','E','Z','Y'];
    $factor = floor((strlen(abs($number)) - 1) / 3) * (abs($number) <=> 1);
    $metricBase = $binary ? 1024 : 1000;

    $number = $number / pow($metricBase, $factor);

    return sprintf("%.{$significantDigits}H", $number) . $prefixes[$factor+8];
}

//  numberToMetric(12345)   => '12.3k'
//  numberToMetric(0.12345) => '123m'