Output current week number within month PHP - php

Question

I have a PHP script to identify the current month and current week within that month.
For today, it should output 501 (i.e. 5th week of the 1st month), however right now it outputs 101.
Can someone explain why this is the case and how I can resolve? I feel I'm missing something obvious.
<?php
date_default_timezone_set("Europe/London");
function weekOfMonthFunction($date) {
$firstOfMonth = date("Y-m-01", strtotime($date));
return intval(date("W", strtotime($date))) - intval(date("W", strtotime($firstOfMonth)));
}
$week = weekOfMonthFunction($date2);
$week = $week + 1;
$month = date("m");
$week_month = $week.$month;
echo $week_month;

Answer 1

<?php
date_default_timezone_set("Europe/London");
function weekOfMonth() {
$now = time();
$week = date('W', $now);
$firstWeekOfMonth = date('W', strtotime(date('Y-m-01', $now)));
return 1 + ($week < $firstWeekOfMonth ? $week : $week - $firstWeekOfMonth);
}
$week = weekOfMonth();
$week_month = $week . date("m");
echo $week_month;
501
Try it online!

Answer 2

You've fixed the date to Y-m-01 instead of Y-m-d from the parameter date.
How about this alternative?
function weekOfMonthFunction($date) {
list($d, $m) = explode('-', date("d-m", strtotime($date)));
return intval(ceil($d/7).str_pad($m, 1, '0', STR_PAD_LEFT));
}
echo weekOfMonthFunction('2021-01-25'); //Give 401
echo weekOfMonthFunction('2020-01-29'); //Gives 501
Explanation:
Date of month divided by 7 rounded up to get week number prepended to month number with a padded 0