<?php 
// 说明：摘录自 User manager for PureFTPd 的大小转换函数 
// 整理：http://www.CodeBit.cn 
 
function DisplayFileSize($filesize) { 
    $array = array( 
        'YB' => 1024 * 1024 * 1024 * 1024 * 1024 * 1024 * 1024 * 1024, 
        'ZB' => 1024 * 1024 * 1024 * 1024 * 1024 * 1024 * 1024, 
        'EB' => 1024 * 1024 * 1024 * 1024 * 1024 * 1024, 
        'PB' => 1024 * 1024 * 1024 * 1024 * 1024, 
        'TB' => 1024 * 1024 * 1024 * 1024, 
        'GB' => 1024 * 1024 * 1024, 
        'MB' => 1024 * 1024, 
        'KB' => 1024, 
    ); 
    if($filesize <= 1024) 
    { 
        $filesize = $filesize . ' B'; 
    } 
    foreach($array AS $name => $size) 
    { 
        if($filesize > $size || $filesize == $size) 
        { 
            $filesize = round((round($filesize / $size * 100) / 100), 0) . ' ' . $name; 
        } 
    } 
    return $filesize; 
} 
 
echo DisplayFileSize( 5145115 ); 
 
?>