Possible errors in session - php

Question

I just want to ask what are the possible errors in SESSION... Because I've been suffering from my bugs! My codes are right but I don't know why it has happened that when I click the submit button it's supposed to pass the value that i declare but it always declare the last value I declared(it means I can't renew the value! once I declared my value that is permanent which is wrong because every time you click the submit it suppose to give new variable)
home.php
<form method="post" action="1home.php">
<label id="checkinD">
<h3>Day</h3>
<Input id="chiD" name="chiD" type="number" min="<?php echo $_SESSION["day_today"]; ?>" max="<?php echo $_SESSION["day_count"]; ?>" required />
</label>
</form>
$chiD = $_POST['chiD'];
$_SESSION["chiD"] = "$chiD";
1home.php
<form method="post" action="2home.php" onsubmit="return validate()">
<label id="checkinD">
<h3>Day</h3>
<Input id="chiD" name="chiD" type="text" value = " <?php echo $_SESSION["chiD"]; ?>" readonly />
</label>
</form>
BTW There is also a crazy one that occurs on my codes it's working very smoothly without logical errors but every 4 hours my codes will have logical errors without my fault!!! it's like automated bugs appeared every hour.
and sometimes to make it work I need to erase the name of my form then replace it again and typed the word that I erased. What kind of shit is this?

Answer 1

PHP, you need to session_start() before assigning values to your
session variables. The date_today variable holds the present datetime, and date_count variable holds a random number.
Though i can not see your full code but here's the working solution.
home.php
<?php
session_start();
$_SESSION["day_today"] = date("Y-m-d H:i:s");
$_SESSION["day_count"] = rand();
?>
<form method="post" action="1home.php">
<label id="checkinD"><h3>Day</h3></label>
<Input id="chiD" name="chiD" type="number" min="<?php echo $_SESSION["day_today"]; ?>" max="<?php echo $_SESSION["day_count"]; ?>" required />
<input type="submit" value="FORM 2" name="btn_form2" >
</form>
home1.php
<?php
session_start();
if(isset($_POST['chiD'])):
$chiD = $_POST['chiD'];
$_SESSION["chiD"] = $chiD;
?>
<form method="post" action="2home.php" onsubmit="return validate()">
<label id="checkinD"><h3>Day</h3></label>
<input id="chiD" name="chiD" type="text" value = "<?php echo $_SESSION["chiD"]; ?>" readonly />
</form>
<?php echo "Day: ". $_SESSION['day_today']; ?>
<br>
<?php echo "Day Count: ". $_SESSION['day_count']; ?>
<?php else: ?>
<h4> Sorry! Somethinh went wrong. </h4>
<?php endif; ?>
Here's a screenshot of the result
Hope this helps