Predefined Constants

The constants below are defined by this extension, and will only be available when the extension has either been compiled into PHP or dynamically loaded at runtime.

Memcached::OPT_COMPRESSION

Enables or disables payload compression. When enabled, item values longer than a certain threshold (currently 2000 bytes) will be compressed during storage and decompressed during retrieval transparently. The threshold can be configured using the memcached.compression_threshold ini setting.

Type: bool, default: true.

Memcached::OPT_COMPRESSION_TYPE

Specifies the compression algorithm to use, if compression is enabled. The valid algorithms are Memcached::COMPRESSION_FASTLZ, Memcached::COMPRESSION_ZLIB and Memcached::COMPRESSION_ZSTD.

Type: int, default: Memcached::COMPRESSION_FASTLZ.

Memcached::COMPRESSION_FASTLZ

The FASTLZ compression algorithm.

Memcached::COMPRESSION_ZLIB

The ZLIB compression algorithm.

Memcached::COMPRESSION_ZSTD

The ZSTD compression algorithm. Available as of Memcached 3.3.0.

Memcached::OPT_COMPRESSION_LEVEL

Specifies the compression level to use, if compression is enabled.

Memcached::COMPRESSION_FASTLZ does not support compression levels.
Memcached::COMPRESSION_ZSTD: minimum level is -22 and maximum level is 22.
Memcached::COMPRESSION_ZLIB: minimum level is 0 and maximum level is 9.

Type: int, default: 3.

Memcached::OPT_SERIALIZER

Specifies the serializer to use for serializing non-scalar values. The valid serializers are Memcached::SERIALIZER_PHP, Memcached::SERIALIZER_IGBINARY, Memcached::SERIALIZER_JSON, Memcached::SERIALIZER_JSON_ARRAY and Memcached::SERIALIZER_MSGPACK.

Type: int, default: Memcached::SERIALIZER_IGBINARY if available, then Memcached::SERIALIZER_MSGPACK if available, then Memcached::SERIALIZER_PHP.

Memcached::SERIALIZER_PHP

The default PHP serializer.

Memcached::SERIALIZER_IGBINARY

The igbinary serializer. Instead of textual representation it stores PHP data structures in a compact binary form, resulting in space and time gains. This serializer is supported only if memcached is configured with --enable-memcached-igbinary option and the igbinary extension is loaded.

Memcached::SERIALIZER_JSON

The JSON serializer. This serializer deserializes JSON to an object.

Memcached::SERIALIZER_JSON_ARRAY

The JSON array serializer. This serializer deserializes JSON to an associative array

Memcached::SERIALIZER_MSGPACK

The » MessagePack serializer. This serializer is supported only if memcached is configured with --enable-memcached-msgpack option and the msgpack extension is loaded.

Memcached::OPT_PREFIX_KEY

This can be used to create a "domain" for your item keys. The value specified here will be prefixed to each of the keys. It cannot be longer than 128 characters and will reduce the maximum available key size. The prefix is applied only to the item keys, not to the server keys.

Type: string, default: "".

Memcached::OPT_HASH

Specifies the hashing algorithm used for the item keys. The valid values are supplied via Memcached::HASH_* constants. Each hash algorithm has its advantages and its disadvantages. Go with the default if you don't know or don't care.

Type: int, default: Memcached::HASH_DEFAULT

Memcached::HASH_DEFAULT

The default (Jenkins one-at-a-time) item key hashing algorithm.

Memcached::HASH_MD5

MD5 item key hashing algorithm.

Memcached::HASH_CRC

CRC item key hashing algorithm.

Memcached::HASH_FNV1_64

FNV1_64 item key hashing algorithm.

Memcached::HASH_FNV1A_64

FNV1_64A item key hashing algorithm.

Memcached::HASH_FNV1_32

FNV1_32 item key hashing algorithm.

Memcached::HASH_FNV1A_32

FNV1_32A item key hashing algorithm.

Memcached::HASH_HSIEH

Hsieh item key hashing algorithm.

Memcached::HASH_MURMUR

Murmur item key hashing algorithm.

Memcached::OPT_DISTRIBUTION

Specifies the method of distributing item keys to the servers. Currently supported methods are modulo and consistent hashing. Consistent hashing delivers better distribution and allows servers to be added to the cluster with minimal cache losses.

Type: int, default: Memcached::DISTRIBUTION_MODULA.

Memcached::DISTRIBUTION_MODULA

Modulo-based key distribution algorithm.

Memcached::DISTRIBUTION_CONSISTENT

Consistent hashing key distribution algorithm (based on libketama).

Memcached::DISTRIBUTION_VIRTUAL_BUCKET

Virtual Bucket hashing key distribution algorithm (also called vbucket).

Memcached::OPT_LIBKETAMA_COMPATIBLE

Enables or disables compatibility with libketama-like behavior. When enabled, the item key hashing algorithm is set to MD5 and distribution is set to be weighted consistent hashing distribution. This is useful because other libketama-based clients (Python, Ruby, etc.) with the same server configuration will be able to access the keys transparently.

Note:
It is highly recommended to enable this option if you want to use consistent hashing, and it may be enabled by default in future releases.

Type: bool, default: false.

Memcached::OPT_LIBKETAMA_HASH

Specifies the hashing algorithm for host mapping.

Type: int.

Memcached::OPT_TCP_KEEPALIVE

Enables TCP keep alive.

Type: bool, default: false.

Memcached::OPT_BUFFER_WRITES

Enables or disables buffered I/O. Enabling buffered I/O causes storage commands to "buffer" instead of being sent. Any action that retrieves data causes this buffer to be sent to the remote connection. Quitting the connection or closing down the connection will also cause the buffered data to be pushed to the remote connection.

Type: bool, default: false.

Memcached::OPT_BINARY_PROTOCOL

Enable the use of the binary protocol. Please note that you cannot toggle this option on an open connection.

Type: bool, default: false.

Memcached::OPT_NO_BLOCK

Enables or disables asynchronous I/O. This is the fastest transport available for storage functions.

Type: bool, default: false.

Memcached::OPT_NOREPLY

Enables or disables ignoring the result of storage commands (set, add, replace, append, prepend, delete, increment, decrement, etc.). Storage commands will be sent without spending time waiting for a reply (there would be no reply). Retrieval commands such as Memcached::get() are unaffected by this setting.

Type: bool, default: false.

Memcached::OPT_TCP_NODELAY

Enables or disables the no-delay feature for connecting sockets (may be faster in some environments).

Type: bool, default: false.

Memcached::OPT_SOCKET_SEND_SIZE

The maximum socket send buffer in bytes.

Type: int, default: varies by platform/kernel configuration.

Memcached::OPT_SOCKET_RECV_SIZE

The maximum socket receive buffer in bytes.

Type: int, default: varies by platform/kernel configuration.

Memcached::OPT_CONNECT_TIMEOUT

In non-blocking mode this set the value of the timeout during socket connection, in milliseconds.

Type: int, default: 1000.

Memcached::OPT_RETRY_TIMEOUT

The amount of time, in seconds, to wait until retrying a failed connection attempt.

Type: int, default: 2.

Memcached::OPT_DEAD_TIMEOUT

The amount of time, in seconds, to wait until retrying dead servers. 0 means no retry.

Type: int, default: 0.

Memcached::OPT_SEND_TIMEOUT

Socket sending timeout, in microseconds. In cases where you cannot use non-blocking I/O this will allow you to still have timeouts on the sending of data.

Type: int, default: 0.

Memcached::OPT_RECV_TIMEOUT

Socket reading timeout, in microseconds. In cases where you cannot use non-blocking I/O this will allow you to still have timeouts on the reading of data.

Type: int, default: 0.

Memcached::OPT_POLL_TIMEOUT

Timeout for connection polling, in milliseconds.

Type: int, default: 1000.

Memcached::OPT_CACHE_LOOKUPS

Enables or disables caching of DNS lookups.

Type: bool, default: false.

Memcached::OPT_SERVER_FAILURE_LIMIT

Specifies the failure limit for server connection attempts. The server will be removed after this many continuous connection failures.

Type: int, default: 5.

Memcached::OPT_SERVER_TIMEOUT_LIMIT

Specifies the timeout limit for server connection attempts. The server will be removed after this many continuous connection timeouts.

Type: int, default: 0.

Memcached::OPT_AUTO_EJECT_HOSTS

Removes disabled servers from the list. Use together with Memcached::OPT_SERVER_FAILURE_LIMIT and Memcached::OPT_SERVER_TIMEOUT_LIMIT.

Note:
This option is replaced by Memcached::OPT_REMOVE_FAILED_SERVERS.

Type: bool, default: false.

Memcached::OPT_VERIFY_KEY

Enables verification of keys by memcached.

Type: bool, default: false.

Memcached::OPT_USE_UDP

Uses UDP instead of TCP.

Type: bool, default: false.

Memcached::OPT_NUMBER_OF_REPLICAS

Stores this many replicas of each item on different servers.

Type: int, default: 0.

Memcached::OPT_RANDOMIZE_REPLICA_READS

Randomizes replica read server.

Type: bool, default: false.

Memcached::OPT_REMOVE_FAILED_SERVERS

Removes disabled servers from the list. Use together with Memcached::OPT_SERVER_FAILURE_LIMIT and Memcached::OPT_SERVER_TIMEOUT_LIMIT.

Type: bool, default: false.

Memcached::HAVE_IGBINARY

Indicates whether igbinary serializer support is available.

Type: bool.

Memcached::HAVE_JSON

Indicates whether JSON serializer support is available.

Type: bool.

Memcached::HAVE_MSGPACK

Indicates whether MessagePack serializer support is available.

Type: bool.

Available as of Memcached 3.0.0.

Memcached::HAVE_ZSTD

Indicates whether ZSTD compression support is available.

Type: bool.

Available as of Memcached 3.3.0.

Memcached::HAVE_ENCODING

Indicates whether data encryption using Memcached::setEncodingKey() is supported.

Type: bool.

Available as of Memcached 3.1.0.

Memcached::HAVE_SESSION

Type: bool.

Available as of Memcached 3.0.0.

Memcached::HAVE_SASL

Type: bool.

Available as of Memcached 3.0.0.

Memcached::GET_EXTENDED

A flag for Memcached::get(), Memcached::getMulti() and Memcached::getMultiByKey() to ensure that the CAS token values are returned as well.

Available as of Memcached 3.0.0.

Memcached::GET_PRESERVE_ORDER

A flag for Memcached::getMulti() and Memcached::getMultiByKey() to ensure that the keys are returned in the same order as they were requested in. Non-existing keys get a default value of null.

Memcached::RES_SUCCESS

The operation was successful.

Memcached::RES_FAILURE

The operation failed in some fashion.

Memcached::RES_HOST_LOOKUP_FAILURE

DNS lookup failed.

Memcached::RES_UNKNOWN_READ_FAILURE

Failed to read network data.

Memcached::RES_PROTOCOL_ERROR

Bad command in memcached protocol.

Memcached::RES_CLIENT_ERROR

Error on the client side.

Memcached::RES_SERVER_ERROR

Error on the server side.

Memcached::RES_WRITE_FAILURE

Failed to write network data.

Memcached::RES_DATA_EXISTS

Failed to do compare-and-swap: item you are trying to store has been modified since you last fetched it.

Memcached::RES_NOTSTORED

Item was not stored: but not because of an error. This normally means that either the condition for an "add" or a "replace" command wasn't met, or that the item is in a delete queue.

Memcached::RES_NOTFOUND