How to create namespace in Aerospike DB from php client

How can one declare a namespace in Aerospike DB for the default PHP client? I have gone through the documentation at http://www.aerospike.com/docs/client/php but cannot find anything useful.

Although you can find the following code at http://www.aerospike.com/docs/operations/configure/namespace

namespace <namespace-name> {
    # memory-size 4G           # 4GB of memory to be used for index and data
    # replication-factor 2     # For multiple nodes, keep 2 copies of the data
    # high-water-memory-pct 60 # Evict non-zero TTL data if capacity exceeds
                               # 60% of 4GB
    # stop-writes-pct 90       # Stop writes if capacity exceeds 90% of 4GB
    # default-ttl 0            # Writes from client that do not provide a TTL
                               # will default to 0 or never expire
    # storage-engine memory    # Store data in memory only
}

but how do I do it with PHP ?