减去两次

Question

我有一个很大的表格，但是其中一些以神秘的方式工作。 乍看之下，下面的方法可以正常工作，将其相减两次并显示正确的值，但是发送到数据库的值是PREVIOUS条目。

我不知道为什么在1个条目中得到2个不同的结果！

<?php
    if (isset($_POST['submit'])) {
        include "DBConnect.php";

        $dag = $dbcon->real_escape_string($_POST['dag']);
        $dato = $dbcon->real_escape_string($_POST['dato']);
        $helligdag = $dbcon->real_escape_string($_POST['helligdag']);
        $plads = $dbcon->real_escape_string($_POST['plads']);
        $frihed = $dbcon->real_escape_string($_POST['frihed']);
        $moedetid = $dbcon->real_escape_string($_POST['moedetid']);
        $fyraften = $dbcon->real_escape_string($_POST['fyraften']);
        $timer = $dbcon->real_escape_string($_POST['timer']);
        $timer50 = $dbcon->real_escape_string($_POST['timer50']);
        $timer100 = $dbcon->real_escape_string($_POST['timer100']);

        mysqli_query($dbcon, "INSERT INTO content
            (dag, dato, helligdag, plads, frihed, moedetid, fyraften, timer, timer50, timer100)
            VALUES ('$dag', '$dato', '$helligdag', '$plads', '$frihed', '$moedetid', '$fyraften', '$timer', '$timer50', '$timer100')");
    }
?>

<?php 
        $timer = '';
        $moedetid = $_POST['moedetid'];
        $fyraften = $_POST['fyraften'];
        $t1 = strtotime($moedetid);
        $t2 = strtotime($fyraften);
        $timer = abs($t2 - $t1) / 3600;
        $timer = intval($timer) . ':' . (($timer - intval($timer)) * 60);
?>

<input type="text" name="timer" value="<?php echo $timer; ?>">