PHP is_writable() function always returns false for a writable directory
After much head-scratching, it transpired that SELinux was preventing the directory from being written to. I found a good tutorial that explains what's going on. I was able to fix it by running this command:
sudo chcon -R -t httpd_sys_rw_content_t tmp
in CentOS 6 above should be SELinux enable enforcing
setenforce Permissivecheck the status
sestatus
to write to a directory you also need execute permissions to the dirs above.
namei -l /var/www/html/limesurvey/tmpshould show which step you do not have the correct permissions for.