1) First we convert timestamp value in to date time format.
<?php
$time = time();
$dateAndTime = date('Y-m-d H:i:s' , $time);
echo $dateAndTime;
?>
1) Second we convert date time in to timestamp value.
<?php
$time = time();
$dateAndTime = date('Y-m-d H:i:s' , $time);
echo $dateAndTime;
?>