Here are some technical details:
PHP has built-in system function tmpfile()
https://php.net/manual/en/function.tmpfile.php
This function Creates a temporary file with a unique name in read-write (w+) mode and returns a file handle. This function asks OS for the location of the user’s temporary folder and tried to create a file there.
After that we use another PHP function is_writable() (https://php.net/manual/en/function.is-writable.php). That function checks if it’s possible to write something to that temporary file.
if file is writable – all ok we proceed.
if file is not writable – we show the error mentioned above.
So please contact you hosting provider and ask why the temporary file created by the tmpfile() function is not writable.
