Firewall-php How to let the program run in the background

Firewall PHP background Run iptables

The following code is the first to allow others to access the network mobile phone, but I want to nohup in 60 minutes after the firewall to remove the records in order to reach someone else every 60 minutes must reconnect to the network.
$iipp =$_server["REMOTE_ADDR"];
EXEC ("iptables-t nat-i prerouting-s $iipp-j ACCEPT");
EXEC ("Nohup sleep 60m >/dev/null 2>&1 &");
EXEC ("Nohup iptables-t nat-d prerouting-s $iipp-j ACCEPT >/dev/null 2>&1 &");
?>

But now the problem is, Nohup does not work, the firewall can not set the time after the automatic deletion of records, I am now a small rookie, ask the big God to help Ah! My brother is grateful!

