/lib/systemd/system/phpsessionclean.service

[Unit]
Description=Clean php session files

[Service]
Type=oneshot
ExecStart=/usr/lib/php/sessionclean
ProtectHome=true
ProtectSystem=true
PrivateTmp=true

See also

• PHP, php-fpm, php -i, PHP sessions, symfony, fastcgi_pass, sessionclean (shell script),phpsessionclean.service (systemd service), phpquery, php.ini, /var/log/php*, PECL, php --help, PHPUnit, Laravel, PHP framework, Composer, phpbrew, Xdebug, php --version, PHP Fatal error, Hello, World! (php)]
• Systemd: systemctl, systemd-journald, journalctl systemd-cat, systemd-logind, systemd-networkd:networkctl, systemd-timesyncd, systemd-resolved, systemd-udevd , Systemd-logind: loginctl, hostnamectl, udevadm, systemd-run, portablectl, systemd-nspawn, systemd resource management, Timer (systemd), systemd logs, /etc/systemd/, systemd services, systemd-mount, /run/systemd/, .service, /usr/lib/systemd/, /usr/lib/systemd/system/, /usr/lib/systemd/system/systemd-resolved.service, /lib/systemd/, machinectl, systemd-oomd, systemd-analyze

https://wiki.ubuntu.com/DebuggingSystemd