防止信号传播到子进程

Question

I have a script toto1.php which call an other script toto2.php in background.

toto1.php

$command = 'nohup php toto2.php > /dev/null 2> /dev/null &';
exec($command);
while (true) {
    echo "sleep...
";
    sleep(1);
}

toto2.php

<?php
function signalHandler($signal)
{
    echo "SIGNAL: $signal
";
    exit;
}
pcntl_signal(SIGINT, 'signalHandler');

for ($i = 0;;$i++) {
    pcntl_signal_dispatch();
    echo "HELLO $i
";
    sleep(1);
}

When I launch toto1.php on a terminal and kill it with ctrl+c, a SIGINT signal is sent to toto2.php. How can I prevent toto1.php to send signal to toto2.php when it is killed?

Regards