Format bytes to kilobytes, megabytes, gigabytes

Scenario: the size of various files are stored in a database as bytes. What's the best way to format this size info to kilobytes, megabytes and gigabytes? For instance I have an MP3 that Ubuntu displays as "5.2 MB (5445632 bytes)". How would I display this on a web page as "5.2 MB" AND have files less than one megabyte display as KB and files one gigabyte and above display as GB?

Solution 1:

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]; 
} 

(Taken from php.net, there are many other examples there, but I like this one best :-)

Solution 2:

This is Chris Jester-Young's implementation, cleanest I've ever seen, combined with php.net's and a precision argument.

function formatBytes($size, $precision = 2)
{
    $base = log($size, 1024);
    $suffixes = array('', 'K', 'M', 'G', 'T');   

    return round(pow(1024, $base - floor($base)), $precision) .' '. $suffixes[floor($base)];
}

echo formatBytes(24962496);
// 23.81M

echo formatBytes(24962496, 0);
// 24M

echo formatBytes(24962496, 4);
// 23.8061M

Solution 3:

Pseudocode:

$base = log($size) / log(1024);
$suffix = array("", "k", "M", "G", "T")[floor($base)];
return pow(1024, $base - floor($base)) . $suffix;

Solution 4:

Just divide it by 1024 for kb, 1024^2 for mb and 1024^3 for GB. As simple as that.