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touch

(PHP 4, PHP 5, PHP 7)

touch — 设定文件的访问和修改时间

说明

bool touch ( string $filename [, int $time = 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 time。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。

参数

filename: 要设定的文件名。
time: 要设定的时间。如果没有提供参数 time 则会使用当前系统的时间。
atime: 如果给出了这个参数，则给定文件的访问时间会被设为 atime，否则会设置为time。如果没有给出这两个参数，则使用当前系统时间。

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	能够修改 Windows 下目录的最后修改时间。

范例

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 ;
}
 ?>

Example #2 使用 time 参数的 touch()

  <?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

在 PHP 5.3.0 之前无法修改 Windows 下目录的最后修改时间。

用户评论:

[#1] csouth at xistins dot com [2014-12-14 08:41:04]

An earlier comment referenced a code snippet that showed file_put_contents() was faster the touch for creating files. I re-ran the same tests on PHP 5.5.9 and this seems to no longer be the case.

<?php $startTime = microtime(true); for($i = 0; $i < 100000; $i++) { file_put_contents('dir/file'.$i, ''); unlink('dir/file'.$i); } echo "Time: ".(microtime(true)-$startTime)."\n"; // Time: 2.6902809143066 $startTime = microtime(true); for($i = 0; $i < 100000; $i++) { touch('dir/file'.$i); unlink('dir/file'.$i); } echo "Time: ".(microtime(true)-$startTime)."\n"; // Time: 2.3343770503998 ?>

[#2] anon [2013-11-10 16:38:56]

Note that when PHP is called by f.e. apache or nginx instead of directly from the command line, touch() will not prefix the location of the invoking script, so the supplied filename must contain an absolute path.

With script started from /home/user/www, this will not touch "/home/user/www/somefile":

<?php touch( 'somefile' ); ?>

But this will:

<?php touch( __DIR__ . '/somefile' ); ?>

[#3] bosslog at gmail dot com [2010-10-08 14:11:13]

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.

[#4] chris dot dallaire at csquaredsystems dot com [2010-04-09 07:41:54]

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.

[#5] ernst at cron-it dot de [2009-09-29 06:38:30]

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

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

[#6] info at archiwumrocka dot art dot pl [2008-12-01 13:59:50]

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"); } } ?>

[#7] mrgrier at yahoo dot com [2008-11-29 10:29:55]

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.

[#8] ddalex at gmail dot com [2008-11-03 09:25:05]

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.

[#9] Radon8472 [2008-08-08 05:07:37]

Important info:

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

[#10] Jeff [2008-06-26 12:29:10]

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);

[#11] Glen [2007-10-18 13:01:58]

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}"); } ?>

[#12] Charles Belov [2006-07-18 18:10:14]

Update the access time without updating the modified time:

Unix command: touch -a filename

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

[#13] spam at webmastersguide dot com [2005-09-01 05:09:00]

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.

[#14] rf_public at yahoo dot co dot uk [2005-07-25 12:19:14]

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

[#15] guy at forster design dot com [2005-05-12 03:42:33]

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.

[#16] feathern at yahoo dot com [2002-08-13 15:31:07]

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;
}

[#17] emilebosch at hotmail dot com [2001-10-06 15:41:56]

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

[#18] master at dreamphp dot com [2001-05-15 11:23:09]

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