Contributed by
Rob Frawley and Nicolas Grekas
in #20858 and #21108.

The Symfony Cache component includes several adapters to support different caching mechanisms such as Redis, APCu, the filesystem, etc. In Symfony 3.3, we added a new adapter for Memcached.

When using it as a component, create first the connection to the Memcached server and then instantiate the new adapter:

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use Symfony\Component\Cache\Adapter\MemcachedAdapter;

$client = MemcachedAdapter::createConnection('memcached://localhost');
$cache = new MemcachedAdapter(\Memcached $client, $namespace = '', $defaultLifetime = 0);

In addition to simple servers, the connection can also be a cluster of Memcached instances with all kinds of custom configuration:

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$client = MemcachedAdapter::createConnection(array(
    // format => memcached://[user:pass@][ip|host|socket[:port]][?weight=int]
    // 'weight' ranges from 0 to 100 and it's used to prioritize servers
    'memcached://my.server.com:11211'
    'memcached://rmf:abcdef@localhost'
    'memcached://127.0.0.1?weight=50'
    'memcached://username:the-password@/var/run/memcached.sock'
    'memcached:///var/run/memcached.sock?weight=20'
));

When used in a Symfony application, it's even simpler to configure and use Memcached:

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# app/config/config_prod.yml
framework:
    cache:
        # defaults to memcached://localhost
        default_memcached_provider: "memcached://my.server.com:11211"
        # ...
        pools:
            app.cache.products:
                adapter: cache.adapter.memcached
                public: true
                # ...

Now you can start storing and fetching items in your Memcached-based cache:

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$cacheProduct = $this->get('app.cache.products')->getItem($productId);
if (!$cacheProduct->isHit()) {
    $product = ...
    $cacheProduct->set($product);
    $this->get('app.cache.products')->save($cacheProduct);
} else {
    $product = $cacheProduct->get();
}