Human-Readable Byte Formatter and Parser

Two complementary jobs that show up constantly: turning a raw byte count into something a human reads at a glance, and turning a config string like 256MB back into an integer for comparison. Doing both with one consistent base-1024 convention avoids the classic bug where one part of the code uses 1000 and another uses 1024 and your limits are quietly off by a few percent.

formatBytes picks the right unit by taking the base-1024 logarithm of the size, clamps it so absurd inputs do not overflow the unit table, then scales and rounds. parseBytes does the inverse with a single regex that captures the numeric part and an optional suffix, mapping the suffix to a power of 1024. Both are pure built-in PHP and round-trip cleanly for whole units.

function formatBytes(int $bytes, int $precision = 2): string {
    $units = ['B', 'KB', 'MB', 'GB', 'TB', 'PB'];
    $bytes = max($bytes, 0);
    $pow = $bytes > 0 ? (int) floor(log($bytes, 1024)) : 0;
    $pow = min($pow, count($units) - 1);
    $value = $bytes / (1024 ** $pow);
    return round($value, $precision) . ' ' . $units[$pow];
}

function parseBytes(string $size): int {
    if (!preg_match('/^([\d.]+)\s*([KMGTP]?B)?$/i', trim($size), $m)) {
        throw new InvalidArgumentException("Bad size: $size");
    }
    $map = ['B' => 0, 'KB' => 1, 'MB' => 2, 'GB' => 3, 'TB' => 4, 'PB' => 5];
    $unit = strtoupper($m[2] ?? 'B');
    return (int) round((float) $m[1] * (1024 ** ($map[$unit] ?? 0)));
}

echo formatBytes(1536) . "\n";          // 1.5 KB
echo formatBytes(5368709120) . "\n";    // 5 GB
echo parseBytes('256 MB') . "\n";       // 268435456
echo parseBytes('1.5GB') . "\n";        // 1610612736