It gives me this error when I run the script: Call to a member function fetch_assoc() on boolean. It is driving me crazy.
I get data from input box like this: 2017-12-14 06:42:10
$sql = "SELECT count(*) as total FROM `purchase` where purchase_datetime BETWEEN str_to_date($date1, 'Y-m-d H:i:s') and str_to_date($date2, 'Y-m-d H:i:s')";
or
$sql = "SELECT count(*) as total FROM `purchase` where purchase_datetime BETWEEN '$date1' and '$date2'";  
or
Trying This:  
$date1 = date('Y-m-d H:i:s', $date1);
$date2 = date('Y-m-d H:i:s', $date2);  
FULL CODE:
            <?php
            if (isset($_POST['submit']) && isset($_POST['date1']) && isset($_POST['date2'])) {
                $date1 = $_POST['date1'];
                $date2 = $_POST['date2'];
                $date1 = date('Y-m-d H:i:s', $date1);
                $date2 = date('Y-m-d H:i:s', $date2);
                $sql = "SELECT count(*) as total FROM `purchase` where purchase_datetime BETWEEN '$date1' and '$date2'";
                $query_result = $conn->query($sql);
                $rows = $query_result->fetch_assoc();
                echo "Result is: " . $rows['total'] . " purchases";
            }
            ?>
 
     
    