Cannot kill a process by a PHP Script running behind nohup

I have a php script that perform some actions after killing some old processes.

act.php

$pids = shell_exec('ps aux | grep "saso" | awk '{print $2}'');
$pids = str_replace("n", ' ', $pids);
$pids = array_filter(explode(' ', $pids));

foreach ($pids as $pid) {
    shell_exec('kill -9 ' . $pid . ' > /dev/null 2>&1 &');
}

// reset of the code . ..

The script works well by running php act.php. It fetch process ids, kill it, then run the reset.

But it is not working when I run nohup php act.php & or nohup php act.php. The process is not killed.

I need nohup to run the script in the background with no hang up.

Can’t PHP script fetch pids behind nohup ? and are there any alternatives ?

Thanks in advance.