PHP » socket_select
socket_select() accepts arrays of sockets and waits for them to change status. Those coming with BSD sockets background will recognize that those socket resource arrays are in fact the so-called file
Due a limitation in the current Zend Engine it is not possible to pass a constant modifier like NULL directly as a parameter to a function which expects this parameter to be passed by reference. Instead use a temporary variable or an expression with the l
| Parameters | Description |
|---|---|
| read | The sockets listed in the read array will be watched to see if characters become available for reading (more precisely, to see if a read will not block - in particular, a socket resource is also ready on end-of-file, in which case a socket_read() will return a zero length string). |
| write | The sockets listed in the write array will be watched to see if a write will not block. |
| except | The sockets listed in the except array will be watched for exceptions. |
| tv_sec | The tv_sec and tv_usec together form the timeout parameter. The timeout is an upper bound on the amount of time elapsed before socket_select() return. tv_sec may be zero , causing socket_select() to return immediately. This is useful for polling. If tv_sec is NULL (no timeout), socket_select() can block indefinitely. |
| tv_usec |
Return Value: On success socket_select() returns the number of socket resources contained in the modified arrays, which may be zero if the timeout expires before anything interesting happens. On error FALSE is returned. The error code can be retrieved with socket_last_error().
Example
<?php
$e = NULL;
if (false === socket_select($r, $w, $e, 0)) {
echo "socket_select() failed, reason: " .
socket_strerror(socket_last_error()) . "
";
}
?>
<?php
/* Prepare the read array */
$read = array($socket1, $socket2);
$write = NULL;
$except = NULL;
$num_changed_sockets = socket_select($read, $write, $except, 0);
if ($num_changed_sockets === false) {
/* Error handling */
} else if ($num_changed_sockets > 0) {
/* At least at one of the sockets something interesting happened */
}
?>
