Insert multiple from input checkbox

[picassoo]

yes, I have problem to insert multiple form in tu tow tabels DB, and how to take the last ID from task to insert in the second tabel task_list_sub Exmp:

task
id = 1
username = Picassoo
title = Test
post_data = 2016-12-22 12:05:00
detaliss = test form here

and in to task_list_sub I need to insert all info, to help picassoo exmp:

id = 1
task_sub_id = 1 --> ID from task
username = Razvan
title = Test
post_data = 2016-12-22 12:05:00

id = 2
task_sub_id = 1 --> ID from task
username = Laura
title = Test
post_data = 2016-12-22 12:05:00
detaliss = test form here