Call to a member function close() on null

Question

Doing a user creation page for a school project.

The code worked perfectly fine when using localhost, but gave the title’s error upon uploading it to a web host.

The error is on the the “$stmt->close();” which I believe is not being called, but not sure why it works internally on my system.

<?php

/* entering localhost config instead
require_once "config.php"; 
*/

define('DB_SERVER', 'localhost');
define('DB_USERNAME', 'root');
define('DB_PASSWORD', '');
define('DB_NAME', 'users');

$mysqli = new mysqli(DB_SERVER, DB_USERNAME, DB_PASSWORD, DB_NAME);

if($mysqli === false){
die("ERROR: Could not connect. " . $mysqli->connect_error);
}

$username = $password = $confirm_password = "";
$username_err = $password_err = $confirm_password_err = "";

if($_SERVER["REQUEST_METHOD"] == "POST"){

if(empty(trim($_POST["username"]))){
    $username_err = "Please enter a username.";
} else{
    $sql = "SELECT id FROM users WHERE username = ?";
    
    if($stmt = $mysqli->prepare($sql)){
        $stmt->bind_param("s", $param_username);
        $param_username = trim($_POST["username"]);
        
        if($stmt->execute()){
            $stmt->store_result();
            
            if($stmt->num_rows == 1){
                $username_err = "This username is already taken.";
            } else{
                $username = trim($_POST["username"]);
            }
        } else{
            echo "Something went wrong.";
        }
    }

    $stmt->close();
}

if(empty(trim($_POST["password"]))){
    $password_err = "Please enter a password.";     
} elseif(strlen(trim($_POST["password"])) < 6){
    $password_err = "Password must have atleast 6 characters.";
} else{
    $password = trim($_POST["password"]);
}

if(empty(trim($_POST["confirm_password"]))){
    $confirm_password_err = "Please confirm password.";     
} else{
    $confirm_password = trim($_POST["confirm_password"]);
    if(empty($password_err) && ($password != $confirm_password)){
        $confirm_password_err = "Password did not match.";
    }
}

if(empty($username_err) && empty($password_err) && empty($confirm_password_err)){
    
    $sql = "INSERT INTO users (username, password) VALUES (?, ?)";
     
    if($stmt = $mysqli->prepare($sql)){
        $stmt->bind_param("ss", $param_username, $param_password);

        $param_username = $username;
        $param_password = password_hash($password, PASSWORD_DEFAULT); 
        
        if($stmt->execute()){
            header("location: login.php");
        } else{
            echo "Something went wrong.";
        }
    }
     
    $stmt->close();
}

$mysqli->close();
}
?>

Solved

Dumb error

Used

declare(strict_types=1); 
error_reporting(-1); 
ini_set('display_errors', 'true');
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);

to find that it was simply a character error in the db config file. Sorry to waste your time.

By the way - The passwords are hashed in the database.

Maybe your `$mysqli->prepare($sql)` fails somehow and returns `null`, but later on you still call `->close()`. Move this `$stmt->close()` inside if — Justinas, Dec 06 '18 at 08:09
Actually it is called but `$stmt` is null. Maybe your credentials have changed from your local db to the remote db and you haven't changed it in your code. — Jules R, Dec 06 '18 at 08:10
Please don't store plain text passwords, have a read about how to use [password_hash()](https://stackoverflow.com/questions/30279321/how-to-use-password-hash) — Nigel Ren, Dec 06 '18 at 08:11

score 0 · Answer 1 · answered Dec 06 '18 at 08:17

You wrote: if($stmt = $mysqli->prepare($sql)){ If the condition does not match $sdmtp will ne null so your $stmt->close(); will fail.

move the line $stmt->close(); into your if execution block.

The other problem you are facing is your confusion about the fact that your code does produce this error on the dev-system (the non-localhost one). This migth be caused by an exception in $mysqli->prepare($sql) on the dev-system.

Call to a member function close() on null

Solved

1 Answers1