mkdir在/ tmp目录中失败

Question

I'm trying to create a folder in php and the code kind of fails each it is used with /tmp/... as path:

exec("mkdir -p /tmp/test/ 2>&1", $output, $return_code);
// $output is empty, $return_code is 0
//mkdir("/tmp/test/"); // Alternative to above

is_dir("/tmp/test/"); // returns true
is_readable("/tmp/test/"); // returns true

But if i check the /tmp -Folder there is no such directory and all subsequent write or read operations on the folder fail, because the folder does not exist. The permissions for /tmp are correct (root:root with 777) and i can do sudo -u http mkdir -p /tmp/test without problems. If I use tmp/test for example, the code will run fine and create a folder within the directory of the php-skript (Which lies in a folder which belongs to me, not the http-user ... )

Any ideas as to why php fails to create a folder under /tmp/ but reports it as being there?

Edit: To specify read- and write-actions: Those actions are not from within my own script, but rather external skripts which get called by the php-script to execute different tasks. Once all of them succeeded, the folder gets zipped and copied somewhere else.

Edit: Right after running exec("mkdir -p /tmp/testfolder");

[daishy@littlezombie tmp]$ pwd
/tmp
[daishy@littlezombie tmp]$ ls -al
insgesamt 8
drwxrwxrwt 21 root   root   440  3. Aug 18:56 .
drwxr-xr-x 20 root   root  4096 10. Jun 16:49 ..
drwxrwxrwt  2 root   root    40  3. Aug 09:42 .font-unix
drwxr-xr-x  2 daishy users   60  3. Aug 14:40 hsperfdata_daishy
drwxrwxrwt  2 root   root    60  3. Aug 09:42 .ICE-unix
drwx------  2 daishy users   60  3. Aug 12:35 kde-daishy
drwx------  2 daishy users  140  3. Aug 18:49 ksocket-daishy
drwx------  3 root   root    60  3. Aug 18:54 systemd-private-5rIfGj
drwx------  3 root   root    60  3. Aug 09:42 systemd-private-HGNW9x
drwx------  3 root   root    60  3. Aug 09:42 systemd-private-od4pyY
drwx------  3 root   root    60  3. Aug 09:42 systemd-private-qAH8UK
drwxrwxrwt  2 root   root    40  3. Aug 09:42 .Test-unix
drwx------  4 daishy users   80  3. Aug 16:55 .Trash-1000
-r--r--r--  1 root   root    11  3. Aug 09:42 .X0-lock
drwxrwxrwt  2 root   root    60  3. Aug 09:42 .X11-unix
drwxrwxrwt  2 root   root    40  3. Aug 09:42 .XIM-unix

Edit: As it turns out, this is not a problem with php, but rather with systemd / apache. In short: systemd creates a private tmp-folder for apache while running, which resides under /tmp/systemd-private-XYZ. So the real /tmp is not viewable by the php-skript, but rather the private one. See http://blog.oddbit.com/post/private-tmp-directories-in-fedora for more infos.

Answer 1

As it turns out, this is not a problem with php, but rather with systemd / apache. In short: systemd creates a private tmp-folder for apache while running, which resides under /tmp/systemd-private-XYZ. So the real /tmp is not viewable by the php-skript, but rather the private one.

To disable this behavior, you can set PrivateTmp=false in /usr/lib/systemd/system/httpd.service

See http://blog.oddbit.com/2012/11/05/fedora-private-tmp/ for more infos.

Answer 2

Don't do that. Use PHP's awesomely called function, tmpfile() . From the docs:

$temp = tmpfile();
fwrite($temp, "writing to tempfile");
fseek($temp, 0);
echo fread($temp, 1024);
fclose($temp); // this removes the file