How to test if a date is between 2 weeks old and current

I am very new to php, and I am trying to figure out how to test if a date is between 2 weeks ago and the current date.

For current date, I know I just use the date() function.

I'm just not sure how to subtract 14 days from the current date, and I haven't been able to find anything discussing this.

Could someone please let me know how I could do this.

Thank you.