title: What is best solution to get next and previous month from given date php
body: <p>I want to get next and previous month from given date. this is my code. </p>
  
  <p>$month = '2011-01-20';</p>
  
  <p>$prevMOnth = funP($month);
  $nextMonth = funN($month);</p>
  
  <p>what is best solution to do that. </p>