PHP

+1 month php

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

php date today plus 1 month

$future_timestamp = strtotime("+1 month");
$data = date('Y-m-d', $future_timestamp);

php days in month

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

in date function + 1 month and - 1 day in php

<?php
$months = n; // Here n = …..-2,-1,0,1,2, …..(months to add or subtract)
$years = n;  // Here n = …..-2,-1,0,1,2, …..(years to add or subtract)
echo date('Y-m-28', mktime(0, 0, 0, date('m')+$months, 1, date('Y') + $years));
?>