filesize

(PHP 4, PHP 5, PHP 7)

filesize — 取得文件大小

说明

filesize ( string $filename ) : int

取得指定文件的大小。

参数

filename

文件的路径。

返回值

返回文件大小的字节数，如果出错返回 FALSE 并生成一条 E_WARNING 级的错误。

Note: 因为 PHP 的整数类型是有符号整型而且很多平台使用 32 位整型，对 2GB 以上的文件，一些文件系统函数可能返回无法预期的结果 。

范例

Example #1 filesize() 例子

<?php

// 输出类似：somefile.txt: 1024 bytes

$filename = 'somefile.txt';
echo $filename . ': ' . filesize($filename) . ' bytes';

?>

错误／异常

失败时抛出E_WARNING警告。

注释

Note: 此函数的结果会被缓存。参见 clearstatcache() 以获得更多细节。

Tip

自 PHP 5.0.0 起, 此函数也用于某些 URL 包装器。请参见 支持的协议和封装协议以获得支持 stat() 系列函数功能的包装器列表。

参见

User Contributed Notes

John Crocker 30-Sep-2019 12:46
The first example given may lead one to assume that this function works with a local filename e.g. $fs = filesize("error_log") but if you manually delete some text, then save and close the file, the next time you check filesize("error_log") it will return the original value, because the value is cached for performance reasons. If you didn't know this, it would look like a nasty bug.

So, everyone tells you to insert clearstatcache() which is supposed to clear the cached value and allow you to retrieve the current file size but it still does nothing and looks like another bug!

However, I found that if you always specify the FULL PATH
e.g. $fs = filesize("/user/some/path/error_log");
then clearstatcache() is not even needed.
PHP-Hasan 12-Jan-2019 05:05
Under Windows 10 filesize obviously cannot work with relative path names. Use absolute path instead. $size = filesize(".\\myfile.txt"); does not work for me while "d:\\MyFiles\\Myfile.txt" will do. The same applys to similar functions like is_file() or stat(). They won't work correctly unless given an absolute path.
Lingasamy Sakthivel 17-Aug-2017 11:27
Using fseek is really slow. This one really better and faster.

    if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
        $size = trim(exec("for %F in (\"" . $file . "\") do @echo %~zF"));
    }
    elseif ((PHP_OS == 'Linux') || (PHP_OS == 'FreeBSD') || (PHP_OS == 'Unix') || (PHP_OS == 'SunOS')) {
        $size = trim(shell_exec("stat -c%s " . escapeshellarg($file)));
    } else {
        $size = filesize($file);
    }
synnus at gmail dot com 26-Jul-2017 02:13
<?php

      // Recover all file sizes larger than > 4GB.
      // Works on php 32bits and 64bits and supports linux
      // Used the com_dotnet extension

     function getSize($file) {
        $size = filesize($file);
        if ($size <= 0)
            if (!(strtoupper(substr(PHP_OS, 0, 3)) == 'WIN')) {
                $size = trim(`stat -c%s $file`);
            }
            else{
                $fsobj = new COM("Scripting.FileSystemObject");
                $f = $fsobj->GetFile($file);
                $size = $f->Size;
            }
        return $size;
    }
?>
Damien Dussouillez 20-Jul-2017 06:25
<?php
/**
 * Return file size (even for file > 2 Gb)
 * For file size over PHP_INT_MAX (2 147 483 647), PHP filesize function loops from -PHP_INT_MAX to PHP_INT_MAX.
 *
 * @param string $path Path of the file
 * @return mixed File size or false if error
 */
function realFileSize($path)
{
    if (!file_exists($path))
        return false;

    $size = filesize($path);
   
    if (!($file = fopen($path, 'rb')))
        return false;
   
    if ($size >= 0)
    {//Check if it really is a small file (< 2 GB)
        if (fseek($file, 0, SEEK_END) === 0)
        {//It really is a small file
            fclose($file);
            return $size;
        }
    }
   
    //Quickly jump the first 2 GB with fseek. After that fseek is not working on 32 bit php (it uses int internally)
    $size = PHP_INT_MAX - 1;
    if (fseek($file, PHP_INT_MAX - 1) !== 0)
    {
        fclose($file);
        return false;
    }
   
    $length = 1024 * 1024;
    while (!feof($file))
    {//Read the file until end
        $read = fread($file, $length);
        $size = bcadd($size, $length);
    }
    $size = bcsub($size, $length);
    $size = bcadd($size, strlen($read));
   
    fclose($file);
    return $size;
}
ivijan dot stefan at gmail dot com 12-Jul-2017 03:02
This function also can be great for browser caching controll. For example, you have a stylesheet and you want to make sure everyone has the most recent version. You could rename it every time you edit it, but that would be a waste of time. Instead, you can do like:

<?php

echo '<link rel="stylesheet" href="style.css?ver=1.'.filesize(dirname(__FILE__).'/style.css').'.'.filemtime(dirname(__FILE__).'/style.css').'.0">';

?>

Sample output:

<link rel="stylesheet" href="style.css?ver=1.8824.1499869132.0">

This also can be apply for JS and also images with same name.
mbh789 at gmail dot com 06-Jul-2017 09:27
function dir_size($file) {
   //tested on win 7x64 php 5.4
    exec('dir /s /a "' . $file.'"', $inf);
    $r=explode(' ',$inf[count($inf)-2]);
    $rr = preg_replace('~[^\d]+~','',$r[count($r)-2]);
    return $rr;
}
contact at evoweb dot fr 31-Jan-2017 10:35
This is an improvement of the function made by Rommel (rommel at rommelsantor dot com).  PHP 5.4+ compatibility and minor calculation of the word to write after the number.
<?php
function human_filesize($bytes, $decimals = 2) {
    $sz = 'BKMGTP';
    $factor = floor((strlen($bytes) - 1) / 3);
    $d = (empty($factor))?0:$decimals;
    return sprintf("%.{$d}f", $bytes / pow(1024, $factor)) . " ". ((!empty($factor))?@$sz[(int)$factor]:"")."o";
}
?>
evgenij at kostanay dot kz 01-Dec-2016 09:05
Slightly edited version of the function from rommel at rommelsantor dot com. Now it returns a two characters file size which is a bit more convenient to read.

<?php
function human_filesize($bytes, $decimals = 2) {
    $factor = floor((strlen($bytes) - 1) / 3);
    if ($factor > 0) $sz = 'KMGT';
    return sprintf("%.{$decimals}f", $bytes / pow(1024, $factor)) . @$sz[$factor - 1] . 'B';
}

print human_filesize(12, 0);                // 12B
print human_filesize(1234567890, 4);        // 1.1498GB
print human_filesize(123456789, 1);            // 117.7MB
print human_filesize(12345678901234, 5);    // 11.22833TB
print human_filesize(1234567, 3);            // 1.177MB
print human_filesize(123456);                // 120.56KB
?>

I removed the P units because strlen doesn't seem to work as expected with integers longer than 14 digits. Though it might be only my system's limitation.
synnus at gmail dot com 03-Nov-2016 12:52
<?php
 // File size for windows
 // if filesize() php > PHP_INT_MAX (4 294 967 296) :: failled
 // filesize_cmd returns the value measured by windows

function filesize_cmd($file) {
    $pth = pathinfo($file);       
    $fz = filesize($file);
    $fx = exec('forfiles /p ' . $pth['dirname'] . ' /m "' . $pth['basename'] . '" /c "cmd /c echo @fsize"');   
    if($fz != $fx) { return $fx; }
    return $fz;
}

?>
jakob dot riishede dot moller at gmail dot com 09-Oct-2016 04:40
"Note: Because PHP's integer type is signed and many platforms use 32bit integers, some filesystem functions may return unexpected results for files which are larger than 2GB."

This ought to be a warning and not a note: filesize - as some of the other comments suggest - is useless for applications where custom action must be taken for large files.
C0nw0nk 04-Jun-2016 06:14
Here is my super fast method of getting >2GB files to output the correct byte size on any version of windows works with both 32Bit and 64Bit.

<?php
function find_filesize($file)
{
    if(substr(PHP_OS, 0, 3) == "WIN")
    {
        exec('for %I in ("'.$file.'") do @echo %~zI', $output);
        $return = $output[0];
    }
    else
    {
        $return = filesize($file);
    }
    return $return;
}

//Usage : find_filesize("path");
//Example :
echo "File size is : ".find_filesize("D:\Server\movie.mp4")."";
?>
synnus at gmail dot com 02-Apr-2016 02:32
// extract filesize with command dir windows 10
// is ok for all system 32/64 and the best compatibility  for Dummy file
// but cant return value in (int) for best return use Float 

<?php

filesize_dir("d:\\test.mkv"); //11.5GB => return (float) 12401880207

function filesize_dir($file) {
    exec('dir ' . $file, $inf);
    $size_raw = $inf[6];
    $size_exp = explode(" ",$size_raw);
    $size_ext = $size_exp[19];
    $size_int = (float) str_replace(chr(255), '', $size_ext);
    return $size_int;
}

?>
synnus at gmail dot com 02-Apr-2016 01:09
// use system windows for give filesize
// best for php 32bit or php 64bit
// I do not know if it works on other windows, but on Windows 10 works well here

<?php

echo filesize_cmd('c:\\', 'log.txt'); //return  1135

function filesize_cmd($folder, $file) {
return exec('forfiles /p '.$folder.' /m "'.$file.'" /c "cmd /c echo @fsize"');
}

?>
synnus at gmail dot com 01-Apr-2016 05:54
// best converting the negative number with File Size .
// does not work with files greater than 4GB
//
// specifically for 32 bit systems. limit conversions filsize is 4GB or
// 4294967296. why we get negative numbers? by what the file
// pointer of the meter must work with the PHP MAX value is 2147483647.
// Offset file : 0 , 1 , 2 , 3 , ... 2147483647 = 2GB
// to go higher up the 4GB negative numbers are used
// and therefore after 2147483647, we will -2147483647
// -2147483647,  -2147483646, -2147483645, -2147483644 ... 0 = 4GB
// therefore 0, 2147483647 and -2147483647 to 0. all done 4GB = 4294967296
// the first offset to 0 and the last offset to 0 of 4GB should be added in
// your compute, so "+ 2" for the number of bytes exate .

<?php
function filsize_32b($file) {
    $filez = filesize($file);
    if($filez < 0) {  return (($filez + PHP_INT_MAX) + PHP_INT_MAX + 2); }
    else { return $filez; }
}
?>
honza dot kuchar at grifart dot cz 05-Feb-2016 09:43
For files bigger then 2 GB use my library called Big File Tools. https://github.com/jkuchar/BigFileTools. More details on stackoverflow: http://stackoverflow.com/a/35233556/631369
Anonymous 21-Nov-2014 04:01
Here a function to get the size of a file in a human understanding way with decimal separator, thousand separator, decimals...

function convertFileSize($file, $size=null, $decimals=2, $dec_sep='.', $thousands_sep=','){
 if (!is_file($file)){
  return "El fichero no existe";
 }
 $bytes = filesize($file);
 $sizes = 'BKMGTP';
 if (isset($size)){
  $factor = strpos($sizes, $size[0]);
  if ($factor===false){
   return "El tama?o debe ser B, K, M, G, T o P";
  }
 } else {
  $factor = floor((strlen($bytes) - 1) / 3);
  $size = $sizes[$factor];
 }
 return number_format($bytes / pow(1024, $factor), $decimals, $dec_sep, $thousands_sep).' '.$size;
}

Source: http://softontherocks.blogspot.com/2014/11/obtener-el-tamano-de-un-fichero-y.html
k dot reznichak at pcpin dot com 24-Sep-2014 10:19
Here ist the very fast and reliable way to get size of large files > 2Gb on 32bit and 64bit platforms.

<?php
  /**
   * Get the size of file, platform- and architecture-independant.
   * This function supports 32bit and 64bit architectures and works fith large files > 2 GB
   * The return value type depends on platform/architecture: (float) when PHP_INT_SIZE < 8 or (int) otherwise
   * @param   resource $fp
   * @return  mixed (int|float) File size on success or (bool) FALSE on error
   */
  function my_filesize($fp) {
    $return = false;
    if (is_resource($fp)) {
      if (PHP_INT_SIZE < 8) {
        // 32bit
        if (0 === fseek($fp, 0, SEEK_END)) {
          $return = 0.0;
          $step = 0x7FFFFFFF;
          while ($step > 0) {
            if (0 === fseek($fp, - $step, SEEK_CUR)) {
              $return += floatval($step);
            } else {
              $step >>= 1;
            }
          }
        }
      } elseif (0 === fseek($fp, 0, SEEK_END)) {
        // 64bit
        $return = ftell($fp);
      }
    }
    return $return;
  }
?>
CertaiN 05-May-2014 07:52
The simplest and most efficient implemention for getting remote filesize:

<?php
function remote_filesize($url) {
    static $regex = '/^Content-Length: *+\K\d++$/im';
    if (!$fp = @fopen($url, 'rb')) {
        return false;
    }
    if (
        isset($http_response_header) &&
        preg_match($regex, implode("\n", $http_response_header), $matches)
    ) {
        return (int)$matches[0];
    }
    return strlen(stream_get_contents($fp));
}
?>
linda dot collins at mailinator dot com 13-Oct-2013 02:08
A fast implementation that determines actual file size of large files (>2GB) on 32-bit PHP:

function RealFileSize($fp)
{
    $pos = 0;
    $size = 1073741824;
    fseek($fp, 0, SEEK_SET);
    while ($size > 1)
    {
        fseek($fp, $size, SEEK_CUR);

        if (fgetc($fp) === false)
        {
            fseek($fp, -$size, SEEK_CUR);
            $size = (int)($size / 2);
        }
        else
        {
            fseek($fp, -1, SEEK_CUR);
            $pos += $size;
        }
    }

    while (fgetc($fp) !== false)  $pos++;

    return $pos;
}

Input is an open file handle.  Return value is an integer for file sizes < 4GB, floating-point otherwise.

This starts out by skipping ~1GB at a time, reads a character in, repeats.  When it gets into the last GB, it halves the size whenever the read fails.  The last couple of bytes are just read in.

Some people might have concerns over this function because $pos will become a floating point number after exceeding integer limits and they know of floating point's tendencies to be inaccurate.  On most computers that correctly implement the IEEE floating point spec, $pos will be accurate out to around 9 *petabytes*.  Unless you are working with multi-petabyte files in PHP or the code is executing on strange hardware, this function is going to be more than sufficient.  Every part of this function has been carefully crafted to deal with 32-bit deficiencies.
cfv1000 at gmail dot com 05-Sep-2013 12:20
To get the filesize of a directory use the built-in function disk_total_space
Arseny Mogilev 16-Aug-2013 10:51
<?php
/**
* Converts bytes into human readable file size.
*
* @param string $bytes
* @return string human readable file size (2,87 Мб)
* @author Mogilev Arseny
*/
function FileSizeConvert($bytes)
{
    $bytes = floatval($bytes);
        $arBytes = array(
            0 => array(
                "UNIT" => "TB",
                "VALUE" => pow(1024, 4)
            ),
            1 => array(
                "UNIT" => "GB",
                "VALUE" => pow(1024, 3)
            ),
            2 => array(
                "UNIT" => "MB",
                "VALUE" => pow(1024, 2)
            ),
            3 => array(
                "UNIT" => "KB",
                "VALUE" => 1024
            ),
            4 => array(
                "UNIT" => "B",
                "VALUE" => 1
            ),
        );

    foreach($arBytes as $arItem)
    {
        if($bytes >= $arItem["VALUE"])
        {
            $result = $bytes / $arItem["VALUE"];
            $result = str_replace(".", "," , strval(round($result, 2)))." ".$arItem["UNIT"];
            break;
        }
    }
    return $result;
}

?>
Anonymous 24-Jul-2013 10:57
This functions returns the exact file size for file larger than 2 GB on 32 bit OS:

<?php
function file_get_size($file) {
    //open file
    $fh = fopen($file, "r");
    //declare some variables
    $size = "0";
    $char = "";
    //set file pointer to 0; I'm a little bit paranoid, you can remove this
    fseek($fh, 0, SEEK_SET);
    //set multiplicator to zero
    $count = 0;
    while (true) {
        //jump 1 MB forward in file
        fseek($fh, 1048576, SEEK_CUR);
        //check if we actually left the file
        if (($char = fgetc($fh)) !== false) {
            //if not, go on
            $count ++;
        } else {
            //else jump back where we were before leaving and exit loop
            fseek($fh, -1048576, SEEK_CUR);
            break;
        }
    }
    //we could make $count jumps, so the file is at least $count * 1.000001 MB large
    //1048577 because we jump 1 MB and fgetc goes 1 B forward too
    $size = bcmul("1048577", $count);
    //now count the last few bytes; they're always less than 1048576 so it's quite fast
    $fine = 0;
    while(false !== ($char = fgetc($fh))) {
        $fine ++;
    }
    //and add them
    $size = bcadd($size, $fine);
    fclose($fh);
    return $size;
}
?>
lito at eordes dot com 06-Mar-2013 03:10
A simple and improved function to get the folder size including subfolders:

<?php
function folderSize ($dir)
{
    $size = 0;
    $contents = glob(rtrim($dir, '/').'/*', GLOB_NOSORT);

    foreach ($contents as $contents_value) {
        if (is_file($contents_value)) {
            $size += filesize($contents_value);
        } else {
            $size += realFolderSize($contents_value);
        }
    }

    return $size;
}

echo folderSize('/var/www/html/').' bytes';
?>
rommel at rommelsantor dot com 19-Nov-2011 12:11
Extremely simple function to get human filesize.
<?php
function human_filesize($bytes, $decimals = 2) {
  $sz = 'BKMGTP';
  $factor = floor((strlen($bytes) - 1) / 3);
  return sprintf("%.{$decimals}f", $bytes / pow(1024, $factor)) . @$sz[$factor];
}
?>
Anonymous 21-Jan-2011 06:58
if you recently appended something to file, and closed it then this method will not show appended data:
<?php
// get contents of a file into a string
$filename = "/usr/local/something.txt";
$handle = fopen($filename, "r");
$contents = fread($handle, filesize($filename));
fclose($handle);
?>
You should insert a call to clearstatcache() before calling filesize()
I've spent two hours to find that =/
frank (at) haua dot net 15-Jan-2011 06:19
I have a cli script running that use the filesize function on a ssh2_sftp connection. It has the >2Gb limit issue, while it does not have that issue locally. I have managed to get around this by doing a "du -sb" command through ssh2_shell.

The following function takes the ssh2_connect resource and the path as input. It may not be neat, but it solves the problem for the moment.

<?php
function fSSHFileSize($oConn, $sPath) {
    if(false !== ($oShell = @ssh2_shell($oConn, 'xterm', null, 500, 24, SSH2_TERM_UNIT_CHARS))) {
        fwrite($oShell, "du -sb '".$sPath."'".PHP_EOL);
        sleep(1);
        while($sLine = fgets($oShell)) {
            flush();
            $aResult[] = $sLine;
        }
        fclose($oShell);
        $iSize = 0;
        if(count($aResult) > 1) {
            $sTemp = $aResult[count($aResult)-2];
            $sSize = substr($sTemp, 0, strpos($sTemp, chr(9)));
            if(is_numeric(trim($sSize))) {
                $iTemp = (int)$sSize;
                if($iTemp > "2000000000") $iSize = $iTemp;
            }
        }
        return $iSize;
    }
    return 0;
}
?>
itsrool at gmail dot com 12-Nov-2009 12:36
My solution for calculating the directory size:

<?php
/**
 * Get the directory size
 * @param directory $directory
 * @return integer
 */
function dirSize($directory) {
    $size = 0;
    foreach(new RecursiveIteratorIterator(new RecursiveDirectoryIterator($directory)) as $file){
        $size+=$file->getSize();
    }
    return $size;
}
?>
tmont 25-Jul-2009 02:05
Here's the best way (that I've found) to get the size of a remote file. Note that HEAD requests don't get the actual body of the request, they just retrieve the headers. So making a HEAD request to a resource that is 100MB will take the same amount of time as a HEAD request to a resource that is 1KB.

<?php
$remoteFile = 'http://us.php.net/get/php-5.2.10.tar.bz2/from/this/mirror';
$ch = curl_init($remoteFile);
curl_setopt($ch, CURLOPT_NOBODY, true);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true); //not necessary unless the file redirects (like the PHP example we're using here)
$data = curl_exec($ch);
curl_close($ch);
if ($data === false) {
  echo 'cURL failed';
  exit;
}

$contentLength = 'unknown';
$status = 'unknown';
if (preg_match('/^HTTP\/1\.[01] (\d\d\d)/', $data, $matches)) {
  $status = (int)$matches[1];
}
if (preg_match('/Content-Length: (\d+)/', $data, $matches)) {
  $contentLength = (int)$matches[1];
}

echo 'HTTP Status: ' . $status . "\n";
echo 'Content-Length: ' . $contentLength;
?>

Result:

HTTP Status: 302
Content-Length: 8808759
Svetoslav Marinov 23-Jul-2009 10:24
This is an updated version of my previous filesize2bytes.
The return type now it's really an int.

<?php
/**
 * Converts human readable file size (e.g. 10 MB, 200.20 GB) into bytes.
 *
 * @param string $str
 * @return int the result is in bytes
 * @author Svetoslav Marinov
 * @author http://slavi.biz
 */
function filesize2bytes($str) {
    $bytes = 0;

    $bytes_array = array(
        'B' => 1,
        'KB' => 1024,
        'MB' => 1024 * 1024,
        'GB' => 1024 * 1024 * 1024,
        'TB' => 1024 * 1024 * 1024 * 1024,
        'PB' => 1024 * 1024 * 1024 * 1024 * 1024,
    );

    $bytes = floatval($str);

    if (preg_match('#([KMGTP]?B)$#si', $str, $matches) && !empty($bytes_array[$matches[1]])) {
        $bytes *= $bytes_array[$matches[1]];
    }

    $bytes = intval(round($bytes, 2));

    return $bytes;
}
?>
Supermagnus 30-Jun-2008 03:38
<?php
function getSizeFile($url) {
    if (substr($url,0,4)=='http') {
        $x = array_change_key_case(get_headers($url, 1),CASE_LOWER);
        if ( strcasecmp($x[0], 'HTTP/1.1 200 OK') != 0 ) { $x = $x['content-length'][1]; }
        else { $x = $x['content-length']; }
    }
    else { $x = @filesize($url); }

    return $x;
}
?>

In case of you have a redirection in the server (like Redirect Permanent in the .htaccess)

In this case we have for exemple:
    [content-length] => Array

        (

            [0] => 294          // Size requested file

            [1] => 357556     // Real Size redirected file

        )
jason dot whitehead dot tas at gmail dot com 08-Feb-2008 03:14
I have created a handy function, using parts of code from kaspernj at gmail dot com and md2perpe at gmail dot com, which should get file sizes > 4GB on Windows, Linux and Mac  (at least).

<?php
    function getSize($file) {
        $size = filesize($file);
        if ($size < 0)
            if (!(strtoupper(substr(PHP_OS, 0, 3)) == 'WIN'))
                $size = trim(`stat -c%s $file`);
            else{
                $fsobj = new COM("Scripting.FileSystemObject");
                $f = $fsobj->GetFile($file);
                $size = $file->Size;
            }
        return $size;
    }
?>
webmaster at eclipse org 07-Nov-2007 07:30
On 64-bit platforms, this seems quite reliable for getting the filesize of files > 4GB

<?php
$a = fopen($filename, 'r');
fseek($a, 0, SEEK_END);
$filesize = ftell($a);
fclose($a);
?>
core58 at mail dot ru 14-Apr-2006 08:21
some notes and modifications to previous post.
refering to RFC, when using HTTP/1.1 your request (either GET or POST or HEAD) must contain Host header string, opposite to HTTP/1.1 where Host ain't required. but there's no sure how your remote server would treat the request so you can add Host anyway (it won't be an error for HTTP/1.0).
host value _must_ be a host name (not CNAME and not IP address).

this function catches response, containing Location header and recursively sends HEAD request to host where we are moved until final response is met.
(you can experience such redirections often when downloading something from php scripts or some hash links that use apache mod_rewrite. most all of dowloading masters handle 302 redirects correctly, so this code does it too (running recursively thru 302 redirections).)

[$counter302] specify how much times your allow this function to jump if redirections are met. If initial limit (5 is default) expired -- it returns 0 (should be modified for your purposes whatever).0
ReadHeader() function is listed in previous post
(param description is placed there too).

<?php
function remote_filesize_thru( $ipAddress, $url, $counter302 = 5 )
{
    $socket = fsockopen( "10.233.225.2", 8080 );
    if( !$socket )
    {
        // failed to open TCP socket connection
        // do something sensible here besides exit();
        echo "<br>failed to open socket for [$ipAddress]";
        exit();
    }
                   
    // just send HEAD request to server
    $head = "HEAD $url HTTP/1.0\r\nConnection: Close\r\n\r\n";
    // you may use HTTP/1.1 instead, then your request head string _must_ contain "Host: " header
    fwrite( $socket, $head );
       
    // read the response header
    $header = ReadHeader( $socket );
    if( !$header )
    {
        // handle empty response here the way you need...
        Header( "HTTP/1.1 404 Not Found" );
        exit();
    }
   
    fclose( $socket );
   
    // check for "Location" header
    $locationMarker = "Location: ";
    $pos = strpos( $header, $locationMarker );
    if( $pos > 0 )
    {
            $counter302--;
            if( $counter302 < 0 )
            {
                     // redirect limit (5 by default) expired -- return some warning or do something sensible here
                    echo "warning: too long redirection sequence";
                    return 0;
            }

            // Location is present -- we should determine target host and move there, like any downloading masters do...
            // no need to use regex here
            $end = strpos( $header, "\n", $pos );
            $location = trim( substr( $header, $pos + strlen( $locationMarker ), $end - $pos - strlen( $locationMarker ) ), "\\r\\n" );
            
             // extract pure host (without "http://")
             $host = explode( "/", $location );
             $ipa = gethostbyname( $host[2] );
             // move to Location
             return remote_filesize_thru( $ipa, $location, $counter302 );
    }
       
    // try to acquire Content-Length within the response
    $regex = '/Content-Length:\s([0-9].+?)\s/';
    $count = preg_match($regex, $header, $matches);
                       
    // if there was a Content-Length field, its value
    // will now be in $matches[1]
    if( isset( $matches[1] ) )
          $size = $matches[1];
    else
          $size = 0;
   
    return $size;
}
?>
aidan at php dot net 12-Jul-2005 09:01
This function quickly calculates the size of a directory:
http://aidanlister.com/repos/v/function.dirsize.php

You can convert filesizes to a human readable size using:
http://aidanlister.com/repos/v/function.size_readable.php

For a faster (unix only) implementation, see function.disk-total-space, note #34100
http://www.php.net/manual/en/function.disk-total-space.php#34100

Also of interest is this wikipedia article, discussing the difference between a kilobyte (1000) and a kibibyte (1024).
http://en.wikipedia.org/wiki/Bytes