How can PHP be used to subtract a month from the current date for database queries?

When working with database queries that involve date calculations, such as subtracting a month from the current date, PHP's date and time functions can be used to achieve this. One way to subtract a month from the current date is by using the `strtotime` function to convert the current date to a Unix timestamp, then subtracting the number of seconds in a month (approximately 30 days), and finally formatting the result back into a date string that can be used in the database query.

$currentDate = date('Y-m-d');
$previousMonthDate = date('Y-m-d', strtotime($currentDate . ' -1 month'));
// $previousMonthDate can now be used in your database query