LP #1520569: creates empty dir after upgrading

After upgrading to innobackupex 2.3.2 an empty directory is created in the same directory where the script is executed

When running the syntax from the command line as root no directory is created, but when running the command from php-cli as root a new empty directory is created each time the script is running

Empty dir:
/var/www/2015-11-21_02-58-58

Version:
innobackupex -v
innobackupex version 2.3.2 Linux (x86_64) (revision id: 306a2e0)

Command line as root:
innobackupex --defaults-file=/var/ini/mysql/my.cnf --user=root --password=xxx --databases="db1 db2 mysql" --stream=tar ./ 2> /var/www/bak/db/innobackupex.log | gzip -c -1 > /var/www/bak/db/2015-11-27-1244_mysql.tar.gz

From php-cli as root:
exec('innobackupex --defaults-file=/var/ini/mysql/my.cnf --user=root --password=xxx --databases="db1 db2 mysql" --stream=tar ./ 2> /var/www/bak/db/innobackupex.log | gzip -c -1 > /var/www/bak/db/2015-11-27-1244_mysql.tar.gz');