pcntl_signal()¶
pcntl_signal() installs a signal handler for a given OS signal. When the specified signal is received by the PHP process, the installed callable is executed.
Common signals include SIGTERM (graceful termination), SIGINT (Ctrl+C interrupt), SIGHUP (reload configuration), and SIGCHLD (child process state change). The constant SIG_DFL restores the default OS handler and SIG_IGN ignores the signal.
Signal handlers are not called immediately when a signal arrives: PHP checks for pending signals between opcodes. Calling pcntl_async_signals(true) enables asynchronous signal dispatching so that handlers run as soon as the signal is received, without waiting for the next opcode boundary.
pcntl_signal() is available only in CLI SAPI and requires the pcntl extension.
<?php
pcntl_async_signals(true);
pcntl_signal(SIGTERM, function (int $signal): void {
echo 'Received SIGTERM, shutting down gracefully.' . PHP_EOL;
// Clean up resources, flush buffers, etc.
exit(0);
});
pcntl_signal(SIGINT, function (int $signal): void {
echo 'Received SIGINT (Ctrl+C).' . PHP_EOL;
exit(0);
});
echo 'Running... send SIGTERM or press Ctrl+C' . PHP_EOL;
while (true) {
sleep(1);
}
?>
See also pcntl_async_signals().
Related : Process Control (pcntl), PHP Handlers, System Event, Process, Command Line Interface (CLI)
