Warning: mysqli_stmt_bind_param() expects parameter 1 to be mysqli_stmt, boolean given? [duplicate]

Answer 1

It seems that you have a missing parameter, you should have 13 parameters and 13 ? check the two parameters after password. (I took out signupdate) try the below :

$stmt = mysqli_prepare(
    $db_conx,
    "INSERT INTO $storenameTable (firstname, lastname, username, address_1, address_2, postcode,  country, county, city, email, password, storeShop) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
);
//after validation, of course
mysqli_stmt_bind_param($stmt, "issi", $firstname, $lastname, $username, $address_1, $address_2, $postcode, $country, $county, $city, $email, $hashedPass, $storenameTable);
mysqli_stmt_execute($stmt);     

You also can get more details on the last error by using var_dump(mysqli_error($db_conx));