Can't write/read from database

Question

I am trying to make a 1 on 1 chat website by learning as I progress, but I've come to a hault.

I can't write to the database.

I have four php files linked below.

Index

Init:

session_start();

define('LOGGED_IN', true);

require 'classes/Core.php';
require 'classes/Chat.php';

?>

Chat

Core:

class Core {
protected $db, $result;
private $rows;

public function __construct() {
    $this->db = new mysqli("localhost","root","");
}

public function query($sql) {
    $this->result = $this->db->query($sql);
}

public function rows() {
    for($x = 1; $x <= $this->db->affected_rows; $x++) {
        $this->rows[] = $this->result->fetch_assoc();
    }
    return $this->rows;
}
 }

?>

I have a MySql database set with WAMP.

P.S. Yes, I have opened the "< ? php" but it doesn't get displayed here.

Is the connection to DB successful? Plz, concentrate upon the erroneous code and don't put unrelated session stuff here. — user4035, Dec 07 '12 at 22:08
Yes, I can connect to the DB. And I don't know which code is erroneous, I wouldn't have posted it all. — user1877016, Dec 07 '12 at 22:09
what do you mean by *can't write to the database*? What happens, what errors are you receiving, what have you tried etc etc etc... — lynks, Dec 07 '12 at 22:15
@lynks On the index file, if you run it, there should be an Array fetched and printed. But I get nothing, not even an error. — user1877016, Dec 07 '12 at 22:17

Olaf Dietsche · Answer 1 · 2012-12-07T22:55:38.047

0

From what I have seen you do not select a default database. You must either give a default database in

$this->db = new mysqli("localhost","root","", "mydatabase");

or select one later with

$this->db->select_db("mydatabase");

You also don't check the return values of the mysql calls. For example, add

public function query($sql) {
    $this->result = $this->db->query($sql);
    if ($this->result === false) {
        echo $this->db->error;
    }
}

after your mysql statements, in order to see whether the statements succeed or fail.

For debugging purposes you can display the sql and corresponding result

public function query($sql) {
    var_dump($sql);
    $this->result = $this->db->query($sql);
    var_dump($this->result);
    echo $this->db->error;
}

edited Dec 07 '12 at 22:55

answered Dec 07 '12 at 22:20

Olaf Dietsche

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I tried that too, setting it as "mysql", but still doesn't work. – user1877016 Dec 07 '12 at 22:23
@user1877016 You must give the name of your database. What's the name, when you connect with phpmyadmin or mysql? – Olaf Dietsche Dec 07 '12 at 22:25
That's the name, it's "mysql". – user1877016 Dec 07 '12 at 22:26
@user1877016 `mysql` is the name of the system database. You should setup a database for your application only. Anyway, look at the updated answer for more. – Olaf Dietsche Dec 07 '12 at 22:33
@user1877016 Still nothing what? If you have an error, the error should be displayed. If you have no error, everything should be fine. You can try debugging your query with `var_dump`. See updated answer. – Olaf Dietsche Dec 07 '12 at 22:56
I get `Fatal error: Cannot redeclare Chat::query() in C:\wamp\www\core\classes\Chat.php on line 27` And the line 27 is the beginning of your code. – user1877016 Dec 07 '12 at 23:01
comment out your old Chat::query definition and try again – user4035 Dec 07 '12 at 23:03
@user1877016 Insert the `var_dump` statements in your `Core::query` method. – Olaf Dietsche Dec 07 '12 at 23:05
Anyway, I have to sleep now. Thank you all for your time. – user1877016 Dec 07 '12 at 23:09
@user1877016 This looks fine so far. Now you do the same for `rows()`, insert `var_dump($this->rows);` after fetching all rows. – Olaf Dietsche Dec 07 '12 at 23:16
@OlafDietsche don't rush with checking query results, cause user1877016 didn't prove, that he really connects to the database. – user4035 Dec 07 '12 at 23:27
@user4035 If he didn't connect, the return value would have been `false` and there should have been shown an error "no database selected". – Olaf Dietsche Dec 07 '12 at 23:35
@OlafDietsche true. He gets nulls for every field of the response. It would be interesting to see the same query results from phpMyAdmin direct connection to the database. – user4035 Dec 07 '12 at 23:50
@user4035 According to http://stackoverflow.com/a/11285967/1741542 this behaviour is correct. – Olaf Dietsche Dec 08 '12 at 00:11

Can't write/read from database

1 Answers1