Symptoms
Attempt to upload any file through File Manager fails with error:
"Unable to upload "fiel01.txt"."" transfer error."
Cause
When file is being uploaded, File Manager first loads it to temp folder on the server it resides, then uploads to destination host by FTP.
The issue takes place because PHP which executes File Manager's script cannot access the temporary files on the server. It happens because the PHP temporary folder is not included into "open_basedir" directive in php.ini.
Resolution
Edit the php.ini file so that folder specified for "upload_tmp_dir" parameter:
upload_tmp_dir = "C:\temp\PHPUpload"
is included in "open_basedir":
open_basedir="C:\CustomerData;C:\PHPUploadData;C:\Program Files (x86)\SWsoft\PEM\sysvhosts\elFinder;C:\Temp\phpupload"