Why not use a database function class in php

Question

I adopted code given in this example: PHP database connection class

But i changed the code with the link above and it is as follows:

class Database {
    public function connect() {
        define('DB_HOST', 'localhost');
        define('DB_NAME', 'university');
        define('DB_USER', 'root');
        define('DB_PASSWORD', 'root');
        $db = mysqli_connect(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);
    }
}
function Information(){
    Database::connect();
    $query = "SELECT * FROM student WHERE id "; $result = mysqli_query($db, $query);
        while($row = mysqli_fetch_array($result)) {
            echo $row['name'];
        }
}
Information();

It gives error:

Notice: Undefined variable: db in /Applications/XAMPP/file.php on line 12.

What could be the reason and what am I doing wrong?

`$db` belongs in the `connect()` function scope. Why not treat `$db` as a class property instead and access it via `$class->db`? — treyBake, Jan 08 '20 at 11:56
`WHERE id ` ?? think it would also be useful to show errors. To get errors out of PHP even in a LIVE environment add these 4 lines to the top of any `MYSQLI_` based script you want to debug `ini_set('display_errors', 1); ini_set('log_errors',1); error_reporting(E_ALL); mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);`. This will force any `MYSQLI_` errors to generate an Exception that you can see on the browser as well as normal PHP errors. — RiggsFolly, Jan 08 '20 at 12:04

score 0 · Accepted Answer · answered Jan 08 '20 at 12:03

Make a property that all methods can share:

<?php

class Database 
{
    private $db;

    public function __construct() 
    {
        define('DB_HOST', 'localhost');
        define('DB_NAME', 'university');
        define('DB_USER', 'root');
        define('DB_PASSWORD', 'root');
        $this->db = mysqli_connect(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);
    }

    public function query($sql)
    {
        return mysqli_query($this->db, $query);
    }
}

And then refactor your function

function Information()
{
    $db = new Database();
    $sql = "SELECT * FROM student WHERE id "; 
    $result = $db->query($sql);
    while($row = mysqli_fetch_array($result)) {
         echo $row['name'];
    }
}

Information();

Danyal Sandeelo · Answer 2 · 2020-01-08T12:13:50.283

-1

The variable db is unknown to the function on this line:

Since $dbis a class property, just create it as a variable in the class

 private $db;

and set it in the connect function as mentioned by delboy1978uk like this:

$this->db = mysqli_connect(DB_HOST,DB_USER,DB_PASSWORD,DB_NAME);

edited Jan 08 '20 at 12:13

answered Jan 08 '20 at 11:59

Danyal Sandeelo

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Your solution will not work as you call `connect()` statically. `$this` won't wiork – delboy1978uk Jan 08 '20 at 12:09
@delboy1978uk updated it – Danyal Sandeelo Jan 09 '20 at 07:36

Why not use a database function class in php

2 Answers2