How to get first date of week in php?

Very simple to use strtotime function:

echo date["Y-m-d", strtotime['monday this week']], "\n";   

echo date["Y-m-d", strtotime['sunday this week']], "\n";

It differs a bit across PHP versions:

Output for 5.3.0 - 5.6.6, php7@20140507 - 20150301, hhvm-3.3.1 - 3.5.1

2015-03-16
2015-03-22

Output for 4.3.5 - 5.2.17

2015-03-23
2015-03-22

Output for 4.3.0 - 4.3.4

2015-03-30
2015-03-29

Comparing at Edge-Cases

Relative descriptions like this week have their own context. The following shows the output for this week monday and sunday when it's a monday or a sunday:

$date = '2015-03-16'; // monday
echo date["Y-m-d", strtotime['monday this week', strtotime[$date]]], "\n";   
echo date["Y-m-d", strtotime['sunday this week', strtotime[$date]]], "\n";

$date = '2015-03-22'; // sunday
echo date["Y-m-d", strtotime['monday this week', strtotime[$date]]], "\n";   
echo date["Y-m-d", strtotime['sunday this week', strtotime[$date]]], "\n";

Againt it differs a bit across PHP versions:

Output for 5.3.0 - 5.6.6, php7@20140507 - 20150301, hhvm-3.3.1 - 3.5.1

2015-03-16
2015-03-22
2015-03-23
2015-03-29

Output for 4.3.5 - 5.0.5, 5.2.0 - 5.2.17

2015-03-16
2015-03-22
2015-03-23
2015-03-22

Output for 5.1.0 - 5.1.6

2015-03-23
2015-03-22
2015-03-23
2015-03-29

Output for 4.3.0 - 4.3.4

2015-03-23
2015-03-29
2015-03-30
2015-03-29

Use strtotime[] function to get the first day of week using PHP. This function returns the default time variable timestamp and then use date[] function to convert timestamp date into understandable date.

strtotime[] Function: The strtotime[] function returns the result in timestamp by parsing the time string.
Syntax:

strtotime[$EnglishDateTime, $time_now]

Parameters: The strtotime[] function accepts two parameters as mentioned above and described below:

• $EnglishDateTime: It specifies the English textual date-time description, which represents the date or time to be returned. The function parses the string and returns the time in seconds. It is required parameter.
• $time_now: This parameter specifies the timestamp used to calculate the returned value. It is an optional parameter.

date[] Function: The date[] function returns more understandable and human readable format of date.
Syntax:

date[ format, timestamp ]

Parameters: This function accepts two parameters as mentioned above and described below:

• format: It specify the format for date and time in which the result will be display.
• timestamp: It is the default time variable from which the date will be generated.

Note: In PHP, the week starts with Monday, so if the time-string is given as “this week” the output will be timestamp of Monday which can make readable by passing it through date[] function.

Program 1: Get the default first day of a week when the time-string is “this week”.

Output:

First day of this week: Monday - 04/02/2019

Now, Usually Sunday is considered as the first day of a week. So, in PHP to get the Sunday of as first day of a week, consider the Sunday of previous week. That is to get the first day [Sunday] of a week need to get the Sunday of previous week and to get the first day [Sunday] of next week need to get the Sunday of this week and so on.
PHP supports -ve indexing in time-string. So, in order to get the previous week it can use the time string as “-1 week” and to get the day it can also have to include the name of the day in time string.

Program 2: Get the first day [Sunday] of the week.

Output:

First day of this week: Sunday - 03/02/2019
First day of last week: Sunday - 27/01/2019
First day of next week: Sunday - 10/02/2019
First day of week after next week : Sunday - 17/02/2019

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