time()
By using time() function in PHP
time() return current timestamp and by adding n days to it lead to time of after n(any number) days
for example :
add 1 days to the current date.
date('Y-m-d',time()+3600*24*1);
add 2 days to the current date.
date('Y-m-d',time()+3600*24*2);
add 3 days to the current date.
date('Y-m-d',time()+3600*24*3);
strtotime()
By using strtotime() function in php
strtotime() function convert string to time .
add 1 days to the current date.
date('Y-m-d',strtotime("+1 days"));
add 2 days to the current date.
date('Y-m-d',strtotime("+2 days"));
add 3 days to the current date.
date('Y-m-d',strtotime("+3 days"));
add 1 days to any date.
date('Y-m-d',strtotime("2021-10-19 +1 days"));
add 2 days on any date.
date('Y-m-d',strtotime("2021-10-19 +2 days"));
add 3 days to any date.
date('Y-m-d',strtotime("2021-10-19 +3 days"));