OOP PHP Errors while querying mysql

Question

I'm just starting with OOP, and while using a tutorial I encountered the following errors:

Warning: Missing argument 2 for MySQLDatabase::query(), called in
/Applications/MAMP/htdocs/object-oriented/public/index.php on line 7 and defined in
/Applications/MAMP/htdocs/object-oriented/includes/database.php on line 28

Notice: Undefined variable: sql in
/Applications/MAMP/htdocs/object-oriented/includes/database.php on line 29

Warning: mysqli_query() expects parameter 1 to be mysqli, null given in
/Applications/MAMP/htdocs/object-oriented/includes/database.php on line 29

Here is my database.php

<?php

require('config.php');

class MySQLDatabase {

    public $connection;

    public function open_connection() {
        $this->$connection = mysqli_connect('DB_SERVER', 'DB_USER', 'DB_PASS');
        if (!$this->connection) {
            die("Database connection failed");
        } else {
            $db_select = mysqli_select_db($this->connection, DB_NAME);
            if (!$select_db) {
                die("Database selection failed");
            }
        }
    }

    public function close_connection() {
        if (isset($this->connection)) {
            mysqli_close($this->connection);
            unset($this->connection);
        }
    }

    public function query($connection, $sql) {
        $result = mysqli_query($this->connection, $sql);
        $this->confirm_query($result);
        return $result;
    }

and my index.php in which I'm trying to test the query() method.

$sql = "INSERT INTO users (id, username, password, first_name, last_name) ";
$sql .= "VALUES (1, 'andrei', 'password', 'Andrei', 'Popa')";
$result = $database->query($sql);

$sql = "SELECT * FROM users WHERE id = 1";
$result_set = $database->query($sql);
$found_user = mysqli_fetch_array($result_set);
echo "Found user!" . $found_user['username'];

Any idea what I'm doing wrong? Thanks

Your query function expects two parameters. You're passing it one - though you don't need to pass it $connection, as it's never used (you're using the object's $connection property instead) — andrewsi
– andrewsi, Commented Dec 16, 2013 at 19:42

BluePsyduck · Accepted Answer · 2013-12-16 19:42:28Z

1

public function query($connection, $sql) {

You don't need the first parameter, as the the connection is property of your class. So only pass $sql into the query method as you already did when using the method:

public function query($sql) {

answered Dec 16, 2013 at 19:42

BluePsyduck

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1 Comment

Popa Andrei Over a year ago

Fixed that. Now I get Warning: mysqli_query() expects parameter 1 to be mysqli, null given in /Applications/MAMP/htdocs/object-oriented/includes/database.php on line 29

Nanne · Accepted Answer · 2013-12-16 19:43:00Z

1

This is your definition:

public function query($connection, $sql) {

and this is your call:

$result = $database->query($sql);

You need to add a connection :)

answered Dec 16, 2013 at 19:43

Nanne

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Comments

BaBL86 · Accepted Answer · 2013-12-16 19:48:44Z

0

You have a number of errors:

First

$db_select = mysqli_select_db($this->connection, DB_NAME);
if (!$select_db) {

check varibables db_select and select_db

Second:

public function query($connection, $sql) {

$result = $database->query($sql);

you need to check your arguments. I think, you need to remove $connection from declaration

public function query($sql) {

because next you are using class variable:

$this->connection;

Third:

public function open_connection()

there is no counstructor in your class and you don't call method open_connection, as a result: you active connection is NULL

You need to add this method to your class:

function __construct() {
    open_connection();
}

answered Dec 16, 2013 at 19:48

BaBL86

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2 Comments

Popa Andrei Over a year ago

Fixed the problems, sorry about $select_db, typo. After using the construct method i end up with: ` Fatal error: Call to undefined function open_connection() in /Applications/MAMP/htdocs/object-oriented/includes/database.php on line 59`

BaBL86 Over a year ago

Sorry, $this->open_connection(); of cause.

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