php-memcached
extension uses the libmemcached
library to provide an API for communicating with memcached servers.
So, This extension requires libmemcached client library.
The steps. Tried successfully from a basic ubuntu:22.04 image:
FROM ubuntu:22.04
RUN apt-get update && apt-get upgrade -y && apt-get install -y net-tools sudo wget nano
And xampp install:
cd /home
sudo wget https://downloadsapachefriends.global.ssl.fastly.net/8.1.6/xampp-linux-x64-8.1.6-0-installer.run
sudo chmod 755 xampp-linux-x64-8.1.6-0-installer.run
sudo ./xampp-linux-x64-8.1.6-0-installer.run
Then, there are a lot of dependencies to install:
sudo apt-get update
sudo apt-get install -y memcached
sudo apt-get install php-pear
sudo apt-get install libcurl3-openssl-dev
sudo apt-get install php-dev
sudo apt-get install zlib1g-dev
sudo apt-get install libmemcached-dev
sudo pecl install memcached #note the path to memcached.so
sudo nano /opt/lampp/etc/php.ini
add extension=/usr/lib/php/20210902/memcached.so #path noted before
sudo /opt/lampp/lampp restart
Or another possible install:
sudo apt-get update
sudo apt-get install autoconf
sudo apt-get install build-essential
sudo apt-get install -y pkg-config
sudo apt-get install zlib1g-dev
sudo apt-get install libmemcached-dev
sudo /opt/lampp/bin/pecl install memcached #note the path to memcached.so
sudo nano /opt/lampp/etc/php.ini
add extension=/opt/lampp/lib/php/extensions/no-debug-non-zts-20210902/memcached.so #path noted before
sudo /opt/lampp/lampp restart
With your code:
$memcached = new Memcached();
$memcached->addServer("127.0.0.1", 8080);
$response = $memcached->get("sample_key");
if($response==true) {
echo $response;
} else {
echo "Cache is empty";
$memcached->set("sample_key", "Sample data from cache") ;
}
Results:
Cache is empty
And phpinfo:

Reference for more details:
https://www.php.net/manual/en/book.memcached.php