Check out example codes for "mysqli count down". It will help you in understanding the concepts better.

Code Example 1

//CALCULATES SECONDS UNTIL THE EVENT
$remaining = $date['date'] - $today;

Code Example 2

<?php 
include("php/db_connect.php");

//TODAY'S DATE
$today = time();

//FETCHES DATE AND TIME FOR THE EVENT FROM DATABASE
$sql = "SELECT * FROM countdown";

$result = mysql_query($sql) or die(mysql_error());

$date = mysql_fetch_array( $result );


//CALCULATES SECONDS UNTIL THE EVENT
$remaining = $date['date'] - $today;

//CALCULATE DAYS UNTIL THE EVENT
$days_remaining = floor($remaining / 86400);

echo "<div class='countdown'> $days_remaining days until event</div>";

?>

Code Example 3

//CALCULATES SECONDS UNTIL THE EVENT
$remaining = strtotime($date['date']) - $today;

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