socket_select

Runs the select() system call on the given arrays of sockets with a specified timeout.

socket_select Function synopsis

socket_select(
    ?array &$read,
    ?array &$write,
    ?array &$except,
    ?int $seconds,
    int $microseconds = 0
  ): int|false

Parameters

$read

Passed by referenceType?array

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 is also ready on end-of-file, in which case a socket_read will return a zero length string).

$write

Passed by referenceType?array

The sockets listed in the $write array will be watched to see if a write will not block.

$except

Passed by referenceType?array

The sockets listed in the $except array will be watched for exceptions.

$seconds

Type?int

The $seconds and $microseconds together form the timeout parameter. The timeout is an upper bound on the amount of time elapsed before socket_select return. $seconds may be zero , causing socket_select to return immediately. This is useful for polling. If $seconds is null (no timeout), socket_select can block indefinitely.

$microseconds

OptionalTypeintDefault value0

Note that the parameters $read, $write, and $except are passed by reference, and contain additional/updated context data that may be useful.

Return value

Typeint|false

On success socket_select returns the number of sockets 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.

Be sure to use the `===` operator when checking for an
error. Since the [`socket_select`](/codex/socket_select) may return 0 the
comparison with `==` would evaluate to `true`: