The checkbox in my form works to put in a true value (1) when the checked and otherwise, the value for the column is false (0).. however, when I run the form without the checkbox checked it gives me this error -
"Notice: Undefined index: publish in C:\xampp\htdocs\phpoop\create_product.php on line 37"
Here is the Product class for creating the product (only including the publish variable)
class Product{
    // database connection and table name
    private $conn;
    private $table_name = "products";
    // object properties
      public $publish;
    public function __construct($db){
        $this->conn = $db;
    }
    // create product
    function create(){
        //write query
        $query = "INSERT INTO
                    " . $this->table_name . "
                SET
                    publish=:publish";
        $stmt = $this->conn->prepare($query);
        // posted values
        $this->publish=htmlspecialchars(strip_tags($this->publish));
        // to get time-stamp for 'created' field
        $this->timestamp = date('Y-m-d H:i:s');
        $this->timestamp2 = date('Y-m-d H:i:s');
        // bind values 
        $stmt->bindParam(":publish", $this->publish);
        if ($stmt->execute()){
            return true;    
        }else{
            return false;
        }
    }
and this is where the form is located for creating the product
// if the form was submitted 
if ($_POST){
    // set product property values
    $product->publish = $_POST['publish'];
    if(isset($_POST['publish'])){
    $published = $_POST['publish'];
    }
    else{
        $published = 0;
    }
    // create the product
    if($product->create()){
        echo "<div class='alert alert-success'>Product was created.</div>";
    }
}
?>
<form action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>" method="post">
  <input type="checkbox" name="publish"  value="1" class="form-control" <?php if(isset($_POST['publish'])) echo "checked='checked'";?>/>
  <button type="submit" class="btn btn-primary">Create Product</button>
 </form>
 
     
    