PHP 的字节格式化函数：byteFormat

function byteFormat($bytes, $unit = "", $decimals = 2) {
	$units = array('B' => 0, 'KB' => 1, 'MB' => 2, 'GB' => 3, 'TB' => 4, 'PB' => 5, 'EB' => 6, 'ZB' => 7, 'YB' => 8);

	$value = 0;
	if ($bytes > 0) {
		// Generate automatic prefix by bytes 
		// If wrong prefix given
		if (!array_key_exists($unit, $units)) {
			$pow = floor(log($bytes)/log(1024));
			$unit = array_search($pow, $units);
		}

		// Calculate byte value by prefix
		$value = ($bytes/pow(1024,floor($units[$unit])));
	}

	// If decimals is not numeric or decimals is less than 0 
	// then set default value
	if (!is_numeric($decimals) || $decimals < 0) {
		$decimals = 2;
	}

	// Format output
	return sprintf('%.' . $decimals . 'f '.$unit, $value);
}

echo byteFormat(4096, "B") ."\n";
echo byteFormat(8, "B", 2) . "\n";
echo byteFormat(1, "KB", 5) . "\n";
echo byteFormat(1073741824, "B", 0) . "\n";
echo byteFormat(1073741824, "KB", 0) . "\n";
echo byteFormat(1073741824, "MB") . "\n";
echo byteFormat(1073741824) . "\n";
echo byteFormat(1073741824, "TB", 10) . "\n";
echo byteFormat(1099511627776, "PB", 6) . "\n";

4096.00 B
8.00 B
0.00098 KB
1073741824 B
1048576 KB
1024.00 MB
1.00 GB
0.0009765625 TB
0.000977 PB