The socket_get_option() function retrieves the value for the option specified by the optname parameter for the socket specified by the socket parameter. socket_get_option() will return FALSE on failure.
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.
表格 1. Available Socket Options
| Option | Description |
|---|---|
| SO_DEBUG | Reports whether debugging information is being recorded. |
| SO_ACCEPTCONN | Reports whether socket listening is enabled. |
| SO_BROADCAST | Reports whether transmission of broadcast messages is supported. |
| SO_REUSEADDR | Reports whether local addresses can be reused. |
| 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. |
| SO_LINGER | Reports whether the socket lingers on socket_close() if data is present. |
| SO_OOBINLINE | Reports whether the socket leaves out-of-band data inline. |
| SO_SNDBUF | Reports send buffer size information. |
| SO_RCVBUF | Reports recieve buffer size information. |
| SO_ERROR | Reports information about error status and clears it. |
| SO_TYPE | Reports the socket type. |
| SO_DONTROUTE | Reports whether outgoing messages bypass the standard routing facilities. |
| SO_RCVLOWAT | Reports the minimum number of bytes to process for socket input operations. ( Defaults to 1 ) |
| SO_RCVTIMEO | Reports the timeout value for input operations. |
| SO_SNDLOWAT | Reports the minimum number of bytes to process for socket output operations. |
| SO_SNDTIMEO | Reports the timeout value specifying the amount of time that an output function blocks because flow control prevents data from being sent. |
注: This function used to be called socket_getopt() prior to PHP 4.3.0