php year and month -1 code example

Example 1: +1 month php

$time = strtotime("2010.12.11");
$final = date("Y-m-d", strtotime("+1 month", $time));

Example 2: php days in month

// For given month
echo cal_days_in_month(CAL_GREGORIAN, 1, 2021);
// For current month
echo date('t');