add x amount of days to a 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)));
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