socket_create_pair

Creates a pair of indistinguishable sockets and stores them in an array

&reftitle.description; `bool` `socket_create_pair` `int` `domain` `int` `type` `int` `protocol` `array` `pair`

`socket_create_pair` creates two connected and indistinguishable sockets, and stores them in `pair`. This function is commonly used in IPC (InterProcess Communication).

&reftitle.parameters;

`domain`

- The `domain` parameter specifies the protocol family to be used by the socket. See `socket_create` for the full list.

`type`

- The `type` parameter selects the type of communication to be used by the socket. See `socket_create` for the full list.

`protocol`

- The `protocol` parameter sets the specific protocol within the specified `domain` to be used when communicating on the returned socket. The proper value can be retrieved by name by using `getprotobyname`. If the desired protocol is TCP, or UDP the corresponding constants `SOL_TCP`, and `SOL_UDP` can also be used.

  See `socket_create` for the full list of supported protocols.

`pair`

- Reference to an array in which the two `Socket` instances will be inserted.

&reftitle.returnvalues;

&return.success;

&reftitle.changelog;

&Version; | &Description;
8.0.0 | `pair` is a reference to an array of `Socket` instances now; previously, it was a reference to an array of `resource`s.

&reftitle.examples;

### `socket_create_pair` example

    <?php
    $sockets = array();

    /* On Windows we need to use AF_INET */
    $domain = (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN' ? AF_INET : AF_UNIX);

    /* Setup socket pair */
    if (socket_create_pair($domain, SOCK_STREAM, 0, $sockets) === false) {
        echo "socket_create_pair failed. Reason: ".socket_strerror(socket_last_error());
    }
    /* Send and Receive Data */
    if (socket_write($sockets[0], "ABCdef123\n", strlen("ABCdef123\n")) === false) {
        echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($sockets[0]));
    }
    if (($data = socket_read($sockets[1], strlen("ABCdef123\n"), PHP_BINARY_READ)) === false) {
        echo "socket_read() failed. Reason: ".socket_strerror(socket_last_error($sockets[1]));
    }
    var_dump($data);

    /* Close sockets */
    socket_close($sockets[0]);
    socket_close($sockets[1]);
    ?>

### `socket_create_pair` IPC example

    <?php
    $ary = array();
    $strone = 'Message From Parent.';
    $strtwo = 'Message From Child.';

    if (socket_create_pair(AF_UNIX, SOCK_STREAM, 0, $ary) === false) {
        echo "socket_create_pair() failed. Reason: ".socket_strerror(socket_last_error());
    }
    $pid = pcntl_fork();
    if ($pid == -1) {
        echo 'Could not fork Process.';
    } elseif ($pid) {
        /*parent*/
        socket_close($ary[0]);
        if (socket_write($ary[1], $strone, strlen($strone)) === false) {
            echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($ary[1]));
        }
        if (socket_read($ary[1], strlen($strtwo), PHP_BINARY_READ) == $strtwo) {
            echo "Received $strtwo\n";
        }
        socket_close($ary[1]);
    } else {
        /*child*/
        socket_close($ary[1]);
        if (socket_write($ary[0], $strtwo, strlen($strtwo)) === false) {
            echo "socket_write() failed. Reason: ".socket_strerror(socket_last_error($ary[0]));
        }
        if (socket_read($ary[0], strlen($strone), PHP_BINARY_READ) == $strone) {
            echo "Received $strone\n";
        }
        socket_close($ary[0]);
    }
    ?>

&reftitle.seealso;

- `socket_create`
- `socket_create_listen`
- `socket_bind`
- `socket_listen`
- `socket_last_error`
- `socket_strerror`