How to export a datetime value from mysql to php

Question

I want to do something like a promotion code feature for my ecomm website. Currently I have a variable called $currentDate which I'm not sure is the correct format.

$currentDate = date("Y-M-D") 

I would like to compare that to a date in my database called expiryDate. In my database I have a row with promoCode = GSS2016 (varchar), discount = 0.1 (double, suppose to represent 10% discount) and expiryDate = 2016-07-28 (datetime which is in YMD if I'm not wrong...) I already have run a query to check if the promocode exist but I'm unsure of how to export it into PHP and to compare it with the current date

$currentDate = date("Y-M-D");

session_start();

$conn = mysqli_connect("localhost", "root", "","websiteDb");

$promoCodeInput = $_POST['promoCode'];

$sql = "SELECT * FROM promocodedb WHERE promoCode = '$promoCodeInput'";

$codeChecker = mysqli_query($conn, $sql) or die (mysqli_error($conn));

if (mysqli_num_rows($codeChecker) > 0)
{
    $fetchDiscount = mysqli_fetch_assoc($codeChecker);

    $expiry = $fetchDiscount['expiryDate'];

    if ($expiry > $currentDate)
    {
        $discountPercentage = $fetchDiscount['discount'];
        echo $discountPercentage;

        $cookie_value = $discountPercentage;
        setcookie("discount", $cookie_value, time() + (60 * 60)); //discount last for 1 hour

        header("Location:cart.php?status=promoApplied");
    }
    else
    {
        //header("Location:cart.php?status=promoExpired");  
    }
}
else
{
    header("Location:cart.php?status=promoFail");   
}

Answer 1

YMD produces a string like 2016-Jul-25 . You cannot compare that reliablly against another string, or even a mysql date/time formatted-string, which would be 2016-07-25 .

String comparison rules will NEVER work properly when comparing numbers/dates:

php > var_dump('2016-Jul-25' > '2016-07-25');
bool(true)
php > var_dump('2016-Jul-25' == '2016-07-25');
bool(false)

Even though those two versions represent the same date, you can see the comparisons come back wrong. By string rules, they're NOT the same dates.

As well, note this one:

php > var_dump('2016-Jul-25' > '2016-Mar-25');
bool(false)

True by human parsing standards, because July comes later in the year than March, but FALSE by string comparison standards, because J comes earlier in the alphabet than M , therefore the Jul version is SMALLER/earlier than the Mar version.

Answer 2

You can transfer all datetime into Unix timestamp and compare between each other as timestamps. Unix timestamp is number of seconds since January 1 1970.

The function for transfering datetime into Unix timestamp is strtotime

This is quite clever function and can recognize many datetime formats.

Look at PHP strtotime