PHP: getting sample code on the first and last day of the week _ PHP Tutorial

PHP obtains the sample code on the first and last days of the week. The code for copying the first and last days of this week is as follows: $ datenewDateTime (); $ date-modify (thisweek); $ first_day_of_week $ date-format (Y-m-d ); $ date-modify (thisweek + 6 // The first and last days of the week

The code is as follows:

$ Date = new DateTime ();
$ Date-> modify ('This Week ');
$ First_day_of_week = $ date-> format ('Y-m-D ');
$ Date-> modify ('this week + 6 days ');
$ End_day_of_week = $ date-> format ('Y-m-D ');

After testing modity, I did not know what to do. I found another two examples.

The code is as follows:

// Monday of the week
// @ $ Timestamp, a timestamp of a week. The default value is the current time.
// @ Is_return_timestamp, whether to return the timestamp; otherwise, the return time format
Function this_monday ($ timestamp = 0, $ is_return_timestamp = true ){
Static $ cache;
$ Id = $ timestamp. $ is_return_timestamp;
If (! Isset ($ cache [$ id]) {
If (! $ Timestamp) $ timestamp = time ();
$ Monday_date = date ('Y-m-D', $ timestamp-86400 * date ('W', $ timestamp) + (date ('W', $ timestamp)> 0? 86400:-/* 6*86400 */518400 ));
If ($ is_return_timestamp ){
$ Cache [$ id] = strtotime ($ monday_date );
} Else {
$ Cache [$ id] = $ monday_date;
}
}
Return $ cache [$ id];
}

// Sunday of the week

The code is as follows:

// @ $ Timestamp, a timestamp of a week. The default value is the current time.
// @ Is_return_timestamp, whether to return the timestamp; otherwise, the return time format
Function this_sunday ($ timestamp = 0, $ is_return_timestamp = true ){
Static $ cache;
$ Id = $ timestamp. $ is_return_timestamp;
If (! Isset ($ cache [$ id]) {
If (! $ Timestamp) $ timestamp = time ();
$ Sunday = this_monday ($ timestamp) +/* 6x86400 */518400;
If ($ is_return_timestamp ){
$ Cache [$ id] = $ Sunday;
} Else {
$ Cache [$ id] = date ('Y-m-D', $ Sunday );
}
}
Return $ cache [$ id];
}

The expiration code is as follows: $ date = new DateTime (); $ date-modify ('this week '); $ first_day_of_week = $ date-format ('Y-m-D '); $ date-modify ('this week + 6...