Php-html drop-down menu selection

Newbie, who is temporarily scheduled to write html, involves filtering issues. The first drop-down menu can be called "type" by default. There are 123456 categories of type, the second drop-down menu is a pile of data found based on the php link mysql. after selecting the first drop-down menu, the second drop-down menu is determined based on the first type, filter out the data to be displayed for the user's second selection. when the query button is clicked, the values of the two drop-down menus need to be transferred to the php backend. please help. thank you for your phphtml data.

Newbie, who is temporarily scheduled to write html, involves filtering issues. The first drop-down menu can be called "type" by default. There are 123456 categories of type, the second drop-down menu is a pile of data found based on the php link mysql. after selecting the first drop-down menu, the second drop-down menu is determined based on the first type, filter out the data that should be displayed for the user's second selection. when the query button is clicked, the values of the two drop-down menus need to be passed to the php backend. please help. thank you.