Filesystem 函数
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touch

(PHP 4, PHP 5)

touch — 设定文件的访问和修改时间

说明

bool touch ( string $filename [, int $time [, int $atime ]] )

尝试将由 filename 给出的文件的访问和修改时间设定为给出的时间。如果没有给出可选参数 time，则使用当前系统时间。如果给出了第三个参数 atime，则给定文件的访问时间会被设为 atime。注意访问时间总是会被修改的，不论有几个参数。

如果文件不存在，则会被创建。成功时返回 TRUE， 或者在失败时返回 FALSE.

Example #1 touch() 例子

<?php
if (touch($FileName)) {
    echo "$FileName modification time has been changed to present time";
} else {
    echo "Sorry, could not change modification time of $FileName";
}
?>

参数

filename

The name of the file being touched.

time

The touch time. If time is not supplied, the current system time is used.

atime

If present, the access time of the given filename is set to the value of atime. Otherwise, it is set to the value passed to the time parameter. If neither are present, the current system time is used.

返回值

成功时返回 TRUE， 或者在失败时返回 FALSE.

更新日志

版本 说明
5.3.0 It became possible to change the modification time of a directory under Windows.

范例

Example #2 touch() example

<?php
if (touch($filename)) {
    echo $filename . ' modification time has been changed to present time';
} else {
    echo 'Sorry, could not change modification time of ' . $filename;
}
?>

Example #3 touch() using the time parameter

<?php
// This is the touch time, we'll set it to one hour in the past.
$time = time() - 3600;

// Touch the file
if (!touch('some_file.txt', $time)) {
    echo 'Whoops, something went wrong...';
} else {
    echo 'Touched file with success';
}
?>

注释

Note:

注意：不同文件系统对时间的判断方法可能是不相同的。

Warning

Prior to PHP 5.3.0 it was not possible to change the modification time of a directory with this function under Windows.

Filesystem 函数
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PHP手册
PHP手册 - N: 设定文件的访问和修改时间

用户评论:

John Doe (08-Apr-2011 08:37)

On Mac OS X, touch() will modify both filectime() and filemtime().

bosslog at gmail dot com (08-Oct-2010 10:11)

I has passed a small test to check which function is faster to create a new file.

file_put_contents vs touch

<?php
for($i = 0; $i < 100; $i++)
{
     file_put_contents('dir/file'.$i, '');
}
?>
Average time: 0,1145s

<?php
for($i = 0; $i < 100; $i++)
{
     touch('dir/file'.$i);
}
?>
Average time: 0,2322s

So, file_put_contents is faster than touch, about two times.

chris dot dallaire at csquaredsystems dot com (09-Apr-2010 03:41)

I needed to use this to touch the /etc/cron.d directory when I updated some files in there. I know the docs say this isn't necessary, but I'm finding that i need to do it in order form my changes to be picked up quickly.

I ran into the permissions error as well and I found that using chmod 777 /etc/cron.d does the trick.

So, you should be able to use the PHP touch function on a directory that has open write access.

Of course, this isn't the most secure approach, but in our application it's not a big deal for that folder to not be super secure.

dotpointer at gmail dot com (15-Feb-2010 11:02)

Regarding the permission error, also discussed in other notes:

Warning: touch() [function.touch]: Utime failed: Operation not permitted in /directory/file.php  on line X

On my system PHP can touch files it does not own as long as the file has at least chmod xx6, BUT it can not set modification time.

This works:

touch('notmyfile');
# -rw-rw-rw-  1 root   root       0 2010-02-15 23:39 notmyfile

This gives error above:

touch('notmyfile', time());
# -rw-rw-rw-  1 root   root       0 2010-02-15 23:39 notmyfile

This works:
touch('notmyfile', time());
# -rw-rw-rw-  1 apache root       0 2010-02-15 23:41 notmyfile

Note that user is APACHE and not NOBODY.
On some systems with apache web server, PHP runs as apache.
To check what user your PHP run as, you may try this to find out:

echo shell_exec('whoami');

ernst at cron-it dot de (29-Sep-2009 02:38)

To touch a file without being owner, it is much easier:

<?php
function touchFile($file) {
  fclose(fopen($file, 'a'));
}
?>

contacto at lucasfonzalida.com.ar (06-Jan-2009 07:44)

This example resolve some drawbacks with DayLight Saving Flag and TimeZone in Windows with native function 'touch()'
See function comments for details

    Usage:
    ------   
<?php   
    // mtime of source File
    $time = filemtime("/source.txt");   

    // Sync mtime at destination file with source file
    betouch("/destination.txt",$time);

    /**
    * Function: Best Effort Touch
    * Update recursively mtime at especified file and verify.
    *
    * This function, resolve 2 drawbacks with native function 'touch()' on Windows:
    * - touch() Return incorrect result (PHP v5.2.5)
    * - touch() Is affected by DayLight Saving Flag and TimeZone
    *
    * @access public  
    * @param  String   $file    Full path to target file
    * @param  int      $time    Unix Timestamp
    * @param  int      $offset  Offset (Default: 0)
    * @return boolean
    */
    function betouch($file, $time, $offset = 0){
        // Add offset to requested mtime
        $new_mtime = $time + $offset;
        // Calling native touch
        $result = touch($file, $new_mtime, $new_mtime);
        // If 'touch()' return OK
        if($result){
            // Clears file status cache
            clearstatcache();
            // Get recently stored mtime at destination file
            $stored_mtime = filemtime($file);
            // Verify if stored is equal to requested mtime
            if($stored_mtime == $time){
                return true;
            }else{
                // Calculate offset between stored mtime and requested mtime
                $offset = $time - $stored_mtime;
                // Recall recursively with new offset and return
                return betouch($file, $time, $offset);
            }
        }
        // Native touch() fail
        return false;
    }
?>

 Lucas Fonzalida
 Buenos Aires - Argentina
 contacto at lucasfonzalida.com.ar

info at archiwumrocka dot art dot pl (01-Dec-2008 09:59)

Only way to change modification date in catalogue is to create file in via touch() and dalete it with unlink():

<?php
$dir    = 'temp';
$files1 = scandir($dir);

$files1 = array_slice($files1, 2);

foreach ($files1 as $key => $val)
{
    if (!is_dir($val)) continue;
    if (!touch($val))
    {
        touch($val . "/plik.txt");
        unlink($val . "/plik.txt");
    }
}
?>

mrgrier at yahoo dot com (29-Nov-2008 06:29)

At least on Linux, touch will not change the time on a symlink itself, but on the file/directory it points to. The only way to work around this is to unlink the symlink, then recreate it.

It took a bit of searching to discover this. The OS itself provides no way to do it. Many people wondered why anyone would want to do this. I use symlinks inside a web tree to point to files outside the web tree. After a certain length of time has passed, I want the symlinks to die, so the files cannot be successfully hotlinked.

ddalex at gmail dot com (03-Nov-2008 05:25)

Actually, Glen is right, PHP won't touch if it is not the current owner of the file, even if the directory and files are writeable by the PHP user.

Bess E. R. Wisser (25-Aug-2008 09:20)

"Glen: In unix on the command-line, you can touch files you don't own - but like other comments on this page state - PHP's built in touch won't work."

No, you can not modify files you don't have write access to in a multi-user environment, ever, under any circumstances. The reason why you fail to do this "in PHP" is because your httpd is most likely running as a "shared" setup, running as nobody/nobody, and your user's files aren't world-writable, and they are not owned by nobody/nobody. Change your required files to be world-writable and you can touch() them, and more.

Radon8472 (08-Aug-2008 01:07)

Important info:

touch() used on a directory always returns FALSE and prints "Permission denied" on NTFS and FAT Filesystem (tested on winXP).

Jeff (26-Jun-2008 08:29)

I've been trying to set a filemtime into the future with touch() on PHP5.

It seems touch $time has a future limit around 1000000 seconds (11 days or so). Beyond this point it reverts to a previous $time.

It doesn't make much sense but I could save you hours of time.

$time = time()+1500000;
touch($cachedfile,$time);

Glen (18-Oct-2007 09:01)

In unix on the command-line, you can touch files you don't own - but like other comments on this page state - PHP's built in touch won't work.

I simple alternative (on unix):

<?php

    function touch_it_good($filename)
    {
        exec("touch {$filename}");
    }
?>

ilrazziatore85 AT yahoo DOT it (21-May-2007 04:10)

Feathern wrote a little script for fetching files from a directory after a certain date.
However the if statement (line 8) should be:

if(($test[2] > 2002) || (($test[2] = 2002) && ($test[0] > 6)) || (($test[2] = 2002) && ($test[0] = 6) && ($test[1] > 17))){
        echo $filelist[$i]."\r\n";
}

Otherwise the script won't fetch lots of files it should.

(In the example given, it should fetch all the files created after 06/17/2002, but the original script would miss files created 03/18/2003 or 11/01/2004)

seocab at rit dot edu (31-Mar-2007 04:09)

The script for modifying the access time without modifying the modified time is overly complicated:

<? touch($filename, date('U', filemtime($filename)), time()); ?>

Since filemtime returns a UNIX timestamp, there is no need to call date('U') so the script could be simplified to:

<? touch($filename,filemtime($filename),time()); ?>

Charles Belov (19-Jul-2006 02:10)

Update the access time without updating the modified time:

Unix command: touch -a filename

PHP: touch(filename, date('U', filemtime(filename)), time())

spam at webmastersguide dot com (01-Sep-2005 01:09)

If you're going to go around deleting (unlinking) files
that you don't own just in order to change the modification
time on the file, you darn well better chown() the file
back to it's original ownership after you are done and
chmod() it back to it's correct permissions.  Otherwise
you will almost certainly break things.  Additionally the
code listed for touch()ing a file you don't own should
set the file creation time back to it's original time if
what is wanted is to just change the modification time.
Also, the code listed will break things if there is an i/o
error such as disk full or too many files in the directory.
Here's how the code SHOULD be written:

Create the new file FIRST, rather than last, with a different
name such as $file.tmp.
Read the ownership, permissions, and creation time of the old file.
Set permissions and creation time of the new file the same as the old.
Rename the new file to the name of the old.
chown() the new file to the user that owned the file it's replacing.

Please be careful adding to the documentation if you've
never taken programming 101.

rf_public at yahoo dot co dot uk (25-Jul-2005 08:19)

Note: the script to touch a file you don't own will change it's owner so ensure permissions are correct or you could lose access to it

guy at forster design dot com (12-May-2005 11:42)

Here's a little workaround that allows the PHP user to touch a file it doesn't own:

<?php

    $target_file = "/path/to/file/filename.txt"; //system filepath to your file
    $file_content = implode("",file($target_file));
    @unlink($target_file);
    if($savetofile = fopen($target_file, "w")) {
        fputs($savetofile, $file_content);
        fclose($savetofile);
    }
    $new_date = strtotime("23 April 2005"); // set the required date timestamp here
    touch($target_file,$new_date);
 
?>

Of course, PHP needs to have write access to the folder containing the file you want to touch, but that should be easy to arrange.

feathern at yahoo dot com (13-Aug-2002 11:31)

Neat little script that will give you a list of all modified files in a certain folder after a certain date:

$filelist = Array();
$filelist = list_dir("d:\\my_folder");
for($i=0;$i<count($filelist);$i++){
    $test = Array();
    $test = explode("/",date("m/d/Y",filemtime($filelist[$i])));
//example of files that are later then
//06/17/2002
    if(($test[2] > 2001) && ($test[1] > 16) && ($test[0] > 5)){
        echo $filelist[$i]."\r\n";
    }
    clearstatcache();
}
function list_dir($dn){
    if($dn[strlen($dn)-1] != '\\') $dn.='\\';
    static $ra = array();
    $handle = opendir($dn);
    while($fn = readdir($handle)){
        if($fn == '.' || $fn == '..') continue;
        if(is_dir($dn.$fn)) list_dir($dn.$fn.'\\');
        else $ra[] = $dn.$fn;
    }
    closedir($handle);
    return $ra;
}

emilebosch at hotmail dot com (06-Oct-2001 11:41)

To spare you ppl couple of hours of valuable time, you can only TOUCH a file that you own! Usually PHP is *nobody*
Warm regards,
Emile Bosch

master at dreamphp dot com (15-May-2001 07:23)

$filename = "test.dat";
if (!file_exists($filename)) {
  touch($filename); // Create blank file
  chmod($filename,0666);
}