errors shown with php ext memcache

[atesin]

Describe the bug
errors when running in console

To Reproduce
just running "php m.php" as suggested

Expected behavior
no errors, a little help would be appreciated instead

Screenshots

PHP Fatal error:  Uncaught Error: Class 'Memcached' not found in /root/setup/memcached-php-backup-restore-master/m.php:27
Stack trace:
#0 /root/setup/memcached-php-backup-restore-master/m.php(235): memcachedTools->__construct('127.0.0.1:11211')
#1 /root/setup/memcached-php-backup-restore-master/m.php(277): runCli(Array)
#2 {main}
  thrown in /root/setup/memcached-php-backup-restore-master/m.php on line 27

Desktop (please complete the following information):
centos8 x86_64, stock nginx + php 7 (php-fpm with unix socket), memcache php ext

Additional context
i think the errors are because the script searches for "memcached" php extension but didn't found
because i have "memcache" (fast, light, simple, efficient, no ext dependencies, does its job, i love it)

my webserver is a little slow because of cookie sessions, i want to switch it to memcache sessions
but i want some level of data persistency... please fix it

(how about a plain shell version?)