when i change calander date how to get the date value in php code example

Example 1: php all date formats

<?php
echo date("F j, Y, g:i a")."<br>";               // March 10, 2001, 5:16 pm
echo date("m.d.y")."<br>";                       // 03.10.01
echo date("j, n, Y")."<br>";                     // 10, 3, 2001
echo date("Ymd")."<br>";                         // 20010310
echo date('h-i-s, j-m-y, it is w Day')."<br>";   // 05-16-18, 10-03-01, 1631 1618 6 Satpm01
echo date('\i\t \i\s \t\h\e jS \d\a\y.')."<br>"; // it is the 10th day.
echo date("D M j G:i:s T Y")."<br>";             // Sat Mar 10 17:16:18 MST 2001
echo date('H:m:s \m \i\s\ \m\o\n\t\h')."<br>";   // 17:03:18 m is month
echo date("H:i:s")."<br>";                       // 17:16:18
echo date("Y-m-d H:i:s")."<br>";                 // 2001-03-10 17:16:18 (the MySQL DATETIME format)

Example 2: change datetime format from Y-m-d h:i:s to d-m-Y in php

$old_date = date('l, F d y h:i:s');              // returns Saturday, January 30 10 02:06:34
$old_date_timestamp = strtotime($old_date);
$new_date = date('Y-m-d H:i:s', $old_date_timestamp);