Export csv data within three months in PHP

Export csv data within three months in PHP, as shown in the following figure:
I want to figure out the first day of the month to the last day of the month three months ago.
What should I do if I can get the first day of three months?

Reply to discussion (solution)

Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-% d ')
Or
Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-01 ')

Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-% d ')
Or
Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-01 ')

No, we use algorithms to calculate the data within a week.

Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-% d ')
Or
Select * fromtbl_namewhere date> = date_format (subdate (now (), INTERVAL 3 month), '% Y-% m-01 ')

No, we use algorithms to calculate the data within a week.

In this case, how can I calculate the data within three months?

Date ("Y-m", strtotime ("-3 month"). "-01"; first day three months ago

Do you have an algorithm for three months? Draw a picture