PHP

php check weekday of date

$dayofweek = date('w', strtotime($date));
$result    = date('Y-m-d', strtotime(($day - $dayofweek).' day', strtotime($date)));

how to get week start date in php

$firstday = date('l - d/m/Y', strtotime("this week"));
echo "First day of this week: ", $firstday;

week day php

date('l'); //Returns full day name of the week: Thursday
date('D'); //Returns abbreviated day name of the week: Thu

php week of a date

Things to be aware of when using week numbers with years.

<?php
echo date("YW", strtotime("2011-01-07")); // gives 201101
echo date("YW", strtotime("2011-12-31")); // gives 201152
echo date("YW", strtotime("2011-01-01")); // gives 201152 too
?>

BUT

<?php
echo date("oW", strtotime("2011-01-07")); // gives 201101
echo date("oW", strtotime("2011-12-31")); // gives 201152
echo date("oW", strtotime("2011-01-01")); // gives 201052 (Year is different than previous example)
?>

Reason:
Y is year from the date
o is ISO-8601 year number
W is ISO-8601 week number of year

Conclusion:
if using 'W' for the week number use 'o' for the year.

php get day of week number

echo date('d', strtotime('2022-02-02')); // 02
echo date('j', strtotime('2022-02-02')); // 2