cal_days_in_month () function is not working

Question

This cal_days_in_month() is not working in PHP version 5.2.11

$days_in_month = cal_days_in_month(0,$month,$year);

Answer 1

Try

date('t', mktime(0, 0, 0, $month, 1, $year)); 

And I found in internet that it require PHP to compile with calender support.

"recompile php with the "--enable-calendar" option."

Answer 2

Having the same problem in a docker container (based on image php:7.4-apache-buster) adding following line in Dockerfile solved the problem:

RUN docker-php-ext-install calendar