Is there a reason why I can't run two or more scripts in parallel in a local host environment? They just simply stop without any error message.
tcp connections have connection timeouts. after some idle time without data on the wire the connection closes and thus the script stops.
php has time_limits additionaly to prevent high cpu usage. but this limit is not directly related to actual seconds but to uses cpu cycles.
for long running scripts its better to run the from command line instead of the browser.
write set_time_limit(0) on the top of you php page and try again
Try below link:
May be it is helpful to you.