I have explained all the steps below and captured data at each stage.
I can't understand why urldecode is not working correctly in this case?
Original String:
  <p>hello</p>
Javascript encodeURIComponent() of above string:
  %3Cp%3E%E2%80%8Bhello%3C%2Fp%3E
Sent via Ajax: 
  %3Cp%3E%E2%80%8Bhello%3C%2Fp%3E
PHP: Echo $_REQUEST['string'];
  %3Cp%3E%E2%80%8Bhello%3C%2Fp%3E
PHP: urldecode of above string
  ​hello
 
    