# socket_get_option

(PHP 4 >= 4.3.0, PHP 5, PHP 7)

socket_get_option — Gets socket options for the socket

### 说明

socket_get_option ( resource `$socket` , int `$level` , int `$optname` ) : mixed

The socket_get_option() function retrieves the value for the option specified by the `optname` parameter for the specified `socket`.

### 参数

`socket`

  A valid socket resource created with socket_create() or socket_accept().

`level`

  The `level` parameter specifies the protocol level at which the option resides. For example, to retrieve options at the socket level, a `level` parameter of `SOL_SOCKET` would be used. Other levels, such as `TCP`, can be used by specifying the protocol number of that level. Protocol numbers can be found by using the getprotobyname() function.

`optname`

  Available Socket Options
  Option | Description | Type
  --- | --- | ---
  `SO_DEBUG` | Reports whether debugging information is being recorded. | int
  `SO_BROADCAST` | Reports whether transmission of broadcast messages is supported. | int
  `SO_REUSEADDR` | Reports whether local addresses can be reused. | int
  `SO_REUSEPORT` | Reports whether local ports can be reused. | int
  `SO_KEEPALIVE` | Reports whether connections are kept active with periodic transmission of messages. If the connected socket fails to respond to these messages, the connection is broken and processes writing to that socket are notified with a SIGPIPE signal. | int
  `SO_LINGER` | Reports whether the `socket` lingers on socket_close() if data is present. By default, when the socket is closed, it attempts to send all unsent data. In the case of a connection-oriented socket, socket_close() will wait for its peer to acknowledge the data. If l_onoff is non-zero and l_linger is zero, all the unsent data will be discarded and RST (reset) is sent to the peer in the case of a connection-oriented socket. On the other hand, if l_onoff is non-zero and l_linger is non-zero, socket_close() will block until all the data is sent or the time specified in l_linger elapses. If the socket is non-blocking, socket_close() will fail and return an error. | array. The array will contain two keys: l_onoff and l_linger.
  `SO_OOBINLINE` | Reports whether the `socket` leaves out-of-band data inline. | int
  `SO_SNDBUF` | Reports the size of the send buffer. | int
  `SO_RCVBUF` | Reports the size of the receive buffer. | int
  `SO_ERROR` | Reports information about error status and clears it. | int (cannot be set by socket_set_option())
  `SO_TYPE` | Reports the `socket` type (e.g. `SOCK_STREAM`). | int (cannot be set by socket_set_option())
  `SO_DONTROUTE` | Reports whether outgoing messages bypass the standard routing facilities. | int
  `SO_RCVLOWAT` | Reports the minimum number of bytes to process for `socket` input operations. | int
  `SO_RCVTIMEO` | Reports the timeout value for input operations. | array. The array will contain two keys: sec which is the seconds part on the timeout value and usec which is the microsecond part of the timeout value.
  `SO_SNDTIMEO` | Reports the timeout value specifying the amount of time that an output function blocks because flow control prevents data from being sent. | array. The array will contain two keys: sec which is the seconds part on the timeout value and usec which is the microsecond part of the timeout value.
  `SO_SNDLOWAT` | Reports the minimum number of bytes to process for `socket` output operations. | int
  `TCP_NODELAY` | Reports whether the Nagle TCP algorithm is disabled. | int
  `MCAST_JOIN_GROUP` | Joins a multicast group. (added in PHP 5.4) | array with keys "group", specifying a string with an IPv4 or IPv6 multicast address and "interface", specifying either an interface number (type int) or a string with the interface name, like "eth0". 0 can be specified to indicate the interface should be selected using routing rules. (can only be used in socket_set_option())
  `MCAST_LEAVE_GROUP` | Leaves a multicast group. (added in PHP 5.4) | array. See `MCAST_JOIN_GROUP` for more information. (can only be used in socket_set_option())
  `MCAST_BLOCK_SOURCE` | Blocks packets arriving from a specific source to a specific multicast group, which must have been previously joined. (added in PHP 5.4) | array with the same keys as `MCAST_JOIN_GROUP`, plus one extra key, source, which maps to a string specifying an IPv4 or IPv6 address of the source to be blocked. (can only be used in socket_set_option())
  `MCAST_UNBLOCK_SOURCE` | Unblocks (start receiving again) packets arriving from a specific source address to a specific multicast group, which must have been previously joined. (added in PHP 5.4) | array with the same format as `MCAST_BLOCK_SOURCE`. (can only be used in socket_set_option())
  `MCAST_JOIN_SOURCE_GROUP` | Receive packets destined to a specific multicast group whose source address matches a specific value. (added in PHP 5.4) | array with the same format as `MCAST_BLOCK_SOURCE`. (can only be used in socket_set_option())
  `MCAST_LEAVE_SOURCE_GROUP` | Stop receiving packets destined to a specific multicast group whose soure address matches a specific value. (added in PHP 5.4) | array with the same format as `MCAST_BLOCK_SOURCE`. (can only be used in socket_set_option())
  `IP_MULTICAST_IF` | The outgoing interface for IPv4 multicast packets. (added in PHP 5.4) | Either int specifying the interface number or a string with an interface name, like eth0. The value 0 can be used to indicate the routing table is to used in the interface selection. The function socket_get_option() returns an interface index. Note that, unlike the C API, this option does NOT take an IP address. This eliminates the interface difference between `IP_MULTICAST_IF` and `IPV6_MULTICAST_IF`.
  `IPV6_MULTICAST_IF` | The outgoing interface for IPv6 multicast packets. (added in PHP 5.4) | The same as `IP_MULTICAST_IF`.
  `IP_MULTICAST_LOOP` | The multicast loopback policy for IPv4 packets, which determines whether multicast packets sent by this socket also reach receivers in the same host that have joined the same multicast group on the outgoing interface used by this socket. This is the case by default. (added in PHP 5.4) | int (either 0 or 1). For socket_set_option() any value will be accepted and will be converted to a boolean following the usual PHP rules.
  `IPV6_MULTICAST_LOOP` | Analogous to `IP_MULTICAST_LOOP`, but for IPv6. (added in PHP 5.4) | int. See `IP_MULTICAST_LOOP`.
  `IP_MULTICAST_TTL` | The time-to-live of outgoing IPv4 multicast packets. This should be a value between 0 (don't leave the interface) and 255. The default value is 1 (only the local network is reached). (added in PHP 5.4) | int between 0 and 255.
  `IPV6_MULTICAST_HOPS` | Analogous to `IP_MULTICAST_TTL`, but for IPv6 packets. The value -1 is also accepted, meaning the route default should be used. (added in PHP 5.4) | int between -1 and 255.

### 返回值

Returns the value of the given option, or `FALSE` on errors.

### 范例

Example #1 socket_get_option() example

    <?php
    $socket = socket_create_listen(1223);

    $linger = array('l_linger' => 1, 'l_onoff' => 1);
    socket_set_option($socket, SOL_SOCKET, SO_LINGER, $linger);

    var_dump(socket_get_option($socket, SOL_SOCKET, SO_REUSEADDR));
    ?>

### 参见

- socket_create_listen() - Opens a socket on port to accept connections
- socket_set_option() - Sets socket options for the socket