An example below on creating a single connection to the default bucket at Couchbase Server:

$cb = new Couchbase("192.168.1.200:8091", "user", "pass");

The Couchbase PHP SDK can also create a persistent connection which can be used for multiple request and response from processes. When you use a persistent connection, the first connection request from an SDK will take longer than subsequent SDK requests. Each subsequent request from a client application automatically reuses the existing instance of the client and the connections for that client. The following example demonstrates how you create a persistent connection:

$cb = new Couchbase("192.168.1.200:8091", "user", "pass", true);

The parameters you use include host:port, username, password, bucket name, and a boolean. The boolean set to true indicates that you want to create a persistent connection. By default connections are not persistent.

When you use a persistent connection, the first request from a client application will typically require more CPU and time to create a connection, compared to operations that rely on an existing connection. Subsequent requests from a client application will automatically reuse this existing persistent connection based upon the name of the connection.

Be aware many web servers such as Apache will automatically take control of the connection instance and may destroy but also rebuild a connection after a certain number of requests. This is part of the web server functioning, and enables the web server to create a pool of reuseable connections.

To plan for redundancy in the event of a failure of the Couchbase Server node you specify to the client library, you may wish to supply multiple hosts. For example:

$hosts = array(
    "server1",
    "server2"
);

$cb = new Couchbase($hosts,
    "user",
    "pass",
    "bucket",
    true);

With this method of building the connection, the client will try each of the hosts specified in the order specified until it either connects with and establishes a connection to a cluster or it runs out of hosts to try.