What does this sentence mean? -Php Tutorial

What does this sentence mean?

strtotime("+$day day $second second +$date")

The complete code is as follows:

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Reply to discussion (solution)

You just need to run it.

Make $ day = $ second = 1
$ Date = '2017-05-09 11:00:00'

Then strtotime ("+ $ day + $ second $ date ")
Is strtotime ("+ 1 day 1 second 11:00:00 ")
Returns a unix timestamp that is one day and one second later than 11:00:00.

strtotime("+$day day $second second +$date")

It refers to the timestamp after $ date $ day $ second seconds.

Http://www.w3school.com.cn/php/func_date_strtotime.asp

Should it be written like this?

strtotime("+$day day $second second",$date)

Should it be written like this?

strtotime("+$day day $second second",$date)

Indicates an error occurred.

Make $ day = $ second = 1
$ Date = '2017-05-09 11:00:00'

Then strtotime ("+ $ day + $ second $ date ")
Is strtotime ("+ 1 day 1 second 11:00:00 ")
Returns a unix timestamp that is later than 11:00:00 on.

strtotime("+$day day $second second +$date")

It refers to the timestamp after $ date $ day $ second seconds.

Http://www.w3school.com.cn/php/func_date_strtotime.asp thanks for answering