add 1 month to date php

PHP
<?php 
// PHP program to add days to $Date 
  
// Declare a date 
$date = "2019-05-10"; 
  
// Add days to date and display it 
echo date('Y-m-d', strtotime($date. ' + 10 days')); 
  
?> $effectiveDate = date('Y-m-d', strtotime("+3 months", strtotime($effectiveDate)));$time = strtotime("2010.12.11");
$final = date("Y-m-d", strtotime("+1 month", $time));<?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));
?>
Source

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