symfony-process/Tests/SignalListener.php

<?php

// required for signal handling
declare (ticks = 1);

pcntl_signal(SIGUSR1, function () {echo 'Caught SIGUSR1'; exit;});

$n = 0;

// ticks require activity to work - sleep(4); does not work
while ($n < 400) {
    usleep(10000);
    ++$n;
}

return;