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pcntl_rfork

PHP function Edit on GitHub ✎

(PHP 8 >= 8.1.0)

Manipulates process resources

Description

pcntl_rfork(int $flags, int $signal = 0): int

Manipulates process resources.

Parameters

flags

The flags parameter determines which resources of the invoking process (parent) are shared by the new process (child) or initialized to their default values.

flags is the logical OR of some subset of:

RFPROC: If set a new process is created; otherwise changes affect the current process.
RFNOWAIT: If set, the child process will be dissociated from the parent. Upon exit the child will not leave a status for the parent to collect.
RFFDG: If set, the invoker's file descriptor table is copied; otherwise the two processes share a single table.
RFCFDG: If set, the new process starts with a clean file descriptor table. Is mutually exclusive with RFFDG.
RFLINUXTHPN: If set, the kernel will return SIGUSR1 instead of SIGCHLD upon thread exit for the child. This is intended to do Linux clone exit parent notification.
RFTSIGZMB: If set, the kernel will deliver the signal specified by the signal parameter to the parent upon the child exit, instead of the default SIGCHLD. Specifying signal number 0 disables signal delivery upon the child exit.
RFTHREAD: If set, the new process shares file descriptor to process leaders table with its parent. Only applies when neither RFFDG nor RFCFDG are set.

signal

The signal number to deliver to the parent when the child exits. This is only used when the RFTSIGZMB flag is set. Specifying 0 disables signal delivery upon the child exit.

Return Values

On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the child's thread of execution. On failure, a -1 will be returned in the parent's context, no child process will be created, and a PHP error is raised.

Examples

pcntl_rfork() example

php

<?php

$pid = pcntl_rfork(RFNOWAIT|RFTSIGZMB, SIGUSR1);
if ($pid > 0) {
  // This is the parent process.
  var_dump($pid);
} else {
  // This is the child process.
  var_dump($pid);
  sleep(2); // as the child does not wait, so we see its "pid"
}
?>

The above example will output something similar to:

output

int(77093)
int(0)

Notes

Note

This function is only available on BSD systems.