Inserting Multiple Row With One Column From Another Table

example data

lot table

id lotno cost

lot-1 BK-12 Php12,000

lot-2 BL-13 Php14,000

lot-3 BG-14 Php15,000

charges table

id name amount

1 Survey fee Php1000

2 Amortization Php2000

3 Monthly Dues Php3000

in my lot_charges form i have charges_id field ONLY

when i add charges to the lot all existing lot will get those charges. example result when i add amortization

result lot_charges table

id lot_id charges_id

1 lot-1 2

2 lot-2 2

3 lot-3 2