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filemtime

(PHP 3, PHP 4, PHP 5)

filemtime -- 取得文件修改时间

说明

int filemtime ( string filename )

返回文件上次被修改的时间，出错时返回 FALSE。时间以 Unix 时间戳的方式返回，可用于 date()。

注: 本函数的结果会被缓存。更多信息参见 clearstatcache()。

提示: 自 PHP 5.0.0 起本函数也可被某些 URL wrapper 使用。参考附录 L 来看哪些 wrapper 支持 stat() 系列函数的功能。

本函数返回文件中的数据块上次被写入的时间，也就是说，文件的内容上次被修改的时间。

例子 1. filemtime() 例子

<?php
// outputs e.g.  somefile.txt was last modified: December 29 2002 22:16:23.
$filename = 'somefile.txt';
if (file_exists($filename)) {
    echo "$filename was last modified: " . date ("F d Y H:i:s.", filemtime($filename));

}
?>

参见 filectime()，stat()，touch() 和 getlastmod()。


add a note add a note User Contributed Notes
madsen at lillesvin dot net
26-Sep-2005 06:39
There are a couple of things to point out about the otherwise great example posted by "notepad at codewalkers dot com".

First of all, as "dma05 at web dot de" pointed out, use HEAD instead of GET - that's being nice to your fellow man.

Second, it will only allow communication on port 80. That can easilly be solved.

<?php
function remote_filemtime($url)
{
   $uri = parse_url($url);
   $uri['port'] = isset($uri['port']) ? $uri['port'] : 80;
   $handle = @fsockopen($uri['host'], $uri['port']);
   // ...
}
?>

But hey, thanks a lot for the function! I've really had great use of it.
dma05 at web dot de
24-Apr-2005 05:25
concerning "notepad at codewalkers dot com"'s code:

this code is pretty neat, but i just wanted to note that using the "HEAD"-method instead of the "GET"-method in the http-request might be preferrable, since then not the whole resource is being downloaded...

http/1.1 definiton snippet:
Section "9.4 HEAD"

 The HEAD method is identical to GET except that the server MUST NOT return a message-body in the response. The metainformation contained in the HTTP headers in response to a HEAD request SHOULD be identical to the information sent in response to a GET request. This method can be used for obtaining metainformation about the entity implied by the request without transferring the entity-body itself. This method is often used for testing hypertext links for validity, accessibility, and recent modification. [...]
-- snippet end ---

the code would then be...:

-- snippet ---
fputs($handle,"HEAD $uri[path] HTTP/1.1\r\nHost: $uri[host]\r\n\r\n");
-- snippet end ---

regards, Magnus
notepad at codewalkers dot com
11-Mar-2005 05:53
i needed the ability to grab the mod time of an image on a remote site. the following is the solution with the help of Joe Ferris.

<?php

function filemtime_remote($uri)
{
   $uri = parse_url($uri);
   $handle = @fsockopen($uri['host'],80);
   if(!$handle)
       return 0;

   fputs($handle,"GET $uri[path] HTTP/1.1\r\nHost: $uri[host]\r\n\r\n");
   $result = 0;
   while(!feof($handle))
   {
       $line = fgets($handle,1024);
       if(!trim($line))
           break;

       $col = strpos($line,':');
       if($col !== false)
       {
           $header = trim(substr($line,0,$col));
           $value = trim(substr($line,$col+1));
           if(strtolower($header) == 'last-modified')
           {
               $result = strtotime($value);
               break;
           }
       }
   }
   fclose($handle);
   return $result;
}
// echo filemtime_remote('http://www.somesite.com/someimage.jpg');

?>
habazi at yahoo dot com
22-Feb-2005 02:13
"this is not (necessarily) correct, the modification time of a directory will be the time of the last file *creation* in a directory (and not in it's sub directories)."

This is not (necessarily) correct either. In *nix the timestamp can be independently set. For example the command "touch directory" updates the timestamp of a directory without file creation.

Also file removal will update the timestamp of a directory.
10-Dec-2004 12:30
A comment below states

  "When using this function to get the modified date of a directory,
   it returns the date of the file in that directory that was last modified."

this is not (necessarily) correct, the modification time of a directory will be the time of the last file *creation* in a directory (and not in it's sub directories).
aidan at php dot net
26-Oct-2004 08:42
If you're looking to convert timestamps to a duration, for example "10" to "10 seconds", or "61" to "1 minute 1 second", try the Duration class.

http://aidan.dotgeek.org/lib/?file=Duration.php
adam at roomvoter dot com
02-May-2004 04:42
The snippet of code earlier that allows you to delete all files older than 2 weeks uses the function (filemtime) - which checks the original create date of the file (filesystem independent).  You MAY want to use filectime() - that looks at when the file was last changed on YOUR file system.

       if (is_dir("$path") )
       {
           $handle=opendir($path);
           while (false!==($file = readdir($handle))) {
               if ($file != "." && $file != "..") { 
                   $Diff = (time() - filectime("$path/$file"))/60/60/24;
                   if ($Diff > 14) unlink("$path/$file");

               }
           }
           closedir($handle);
       }
wookie at at no-way dot org
15-Sep-2003 05:17
Another little handy tool; to get the most recent modified time from files in a directory. It even does recursive directories if you set the $doRecursive param to true. Based on a file/directory list function I saw somewhere on this site. ;)

function mostRecentModifiedFileTime($dirName,$doRecursive) {
   $d = dir($dirName);
   $lastModified = 0;
   while($entry = $d->read()) {
       if ($entry != "." && $entry != "..") {
           if (!is_dir($dirName."/".$entry)) {
               $currentModified = filemtime($dirName."/".$entry);
           } else if ($doRecursive && is_dir($dirName."/".$entry)) {
               $currentModified = mostRecentModifiedFileTime($dirName."/".$entry,true);
           }
           if ($currentModified > $lastModified){
               $lastModified = $currentModified;
           }
       }
   }
   $d->close();
   return $lastModified;
}
paranoid at dds dot nl
05-Jun-2003 08:43
To get the last modification time of a directory, you can use this:

<pre>
$getLastModDir = filemtime("/path/to/directory/.");
</pre>

Take note on the last dot which is needed to see the directory as a file and to actually get a last modification date of it.

This comes in handy when you want just one 'last updated' message on the frontpage of your website and still taking all files of your website into account.

Regards,
Frank Keijzers
laurent dot pireyn at wanadoo dot be
27-Sep-2001 08:00
If you use filemtime with a symbolic link, you will get the modification time of the file actually linked to. To get informations about the link self, use lstat.
24-Aug-2001 10:08
When using this function to get the modified date of a directory, it returns the date of the file in that directory that was last modified.
jay at fudge dot org
30-Jun-1999 04:55
If you want this functionality for the parent web page you should use getlastmod()
i.e.
<?php echo "Last modified: ".date( "F d Y H:i:s.", getlastmod() ); ?>
within the included page... i.e. as a commont footer include for all pages
gerardj at home dot com
20-May-1999 11:27
The above code works fine if you place it on each page you want a date stamp on.  I've found that if you place a reference such as filemtime(__FILE__) in an included or required file, that the modification time of the inherited file will be returned, not the time of the file that did the ineriting.
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