touch()

(PHP 4, PHP 5, PHP 7)

设定文件的访问和修改时间

说明

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

要设定的文件名。

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。

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

范例

Example #1touch()例子

使用$time参数的touch()

Average time: 0,1145s

Average time: 0,2322s
So, file_put_contents is faster than touch, about two times.

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

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

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.

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

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.

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.

A better explanation:
For file $file and UNIX time stored in vars $access and $modified
- change only access time
\touch($file, \filemtime($file), $access);
- change only modified time
\touch($file, $modified, \fileatime($file));
- change both access and modified time
\touch($file, $modified, $access);
Seeing the results:
//use a session cookie stored in a custom folder
$file = '/var/www/test_com/session/sess_qfn587cudfpgsijm1bs4d81s75';
echo 'stats for sess_qfn587cudfpgsijm1bs4d81s75
';
\clearstatcache();
echo 'access: '.\date("Y-m-d H:i:s", \fileatime($file)).'
';
echo 'modified: '.\date("Y-m-d H:i:s", \filemtime($file)).'
';
echo 'change access to now, modified +1 hour
';
\touch($x, \filemtime($file)+3600, time());
\clearstatcache();
echo 'access: '.\date("Y-m-d H:i:s", \fileatime($file)).'
';
echo 'modified: '.\date("Y-m-d H:i:s", \filemtime($file)).'
';
Notice the double call to clearstatcache()!

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): 

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

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

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.

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;$i 2001) && ($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;
}

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. 

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