javascript - Updating php values using jquery -

<?php $date="2016-01-01";  ?> <script type="javascript">        $(document).ready(function(){               $('#prev').click(function(){               var myvar2=<?php echo json_encode($date);?>;               alert(myvar2);               var myvar=<?php $date2=date('y-m-d',strtotime('-1 day',strtotime($date))); $date=$date2; echo json_encode($date); ?>;               alert(myvar);               myvar2=<?php echo json_encode($date);?>;               alert(myvar2);               }        }) </script> <input type="button" value="prev" id="prev" /> 

i need decrement value of variable date every time button id="prev" clicked. problem here value of variable date not getting updated

if using sessions, need ajax call call php file within session update particular session variable. issue @ hand though not update until next time base page loaded since information need accessed.

in sample, need page say:

session_start(); 

and like:

$date = isset($_session["date"]) ? $_session["date"] : "2016-01-01"; 

and on front end need ajax post request file data key being "date":

session_start(); $_session["date"] = $_post["date"]; 

then each time load page, long session maintained keep date, default value being: "2016-01-01"