日期函数中的第二个参数是什么意思？

Question

Can anyone please explain me the second argument of date function ?

string date ( string $format [, int $timestamp = time() ] )

What is it do,I mean what is it meant for ? I never used it except today when I had to do the following :

echo date('Y-m-d',strtotime('+1 day'));

Answer 1

By default date() assumes you are referring to "now". If you want to use date with any other datetime other than "no" then you need to specify it using a timestamp.

var_dump(date("Y-m-d") === date("Y-m-d", time())); // bool(true)