Why Am I Getting a \"500 Internal Server Error\" When Accessing a MySQLi Connection from a Separate Class in PHP?

How to Access MySQLi from a Separate Class in PHP

You are encountering an error when attempting to establish a database connection from a separate class in PHP using MySQLi. The error is "Internal Server Error 500" when you try to access the connection object, indicating a problem with your code or configuration.

To resolve this issue, let's analyze the code and identify key points:

Database Class:

The database class contains the necessary information for connecting to the database, such as the server name, user name, password, and database name.

API Class:

Within the API class, you initialize the $db property with new Database(). This establishes a new database connection object, which is different from the connection created within the __construct method of the database class.

Function Call:

You are then attempting to execute a query using the $this->db->conn object, which is undefined within the MyAPI class. This is because the $conn property is only defined within the Database class.

Solution:

To access the database connection object within the MyAPI class, you need to pass it as a constructor argument when creating a new instance of Database.

Here's the corrected code:

Database.php:

<code class="php">class Database
{
    private $conn;

    public function __construct()
    {
        $this->conn = new mysqli(...connection details...);
    }

    public function getConn()
    {
        return $this->conn;
    }
}</code>

MyAPI.php:

<code class="php">class MyAPI
{
    private $db;

    public function __construct($db)
    {
        $this->db = $db;
    }

    public function getUser($id)
    {
        $sql = ...query...;
        $result = mysqli_query($this->db->getConn(), $sql);
        return mysqli_fetch_assoc($result);
    }
}</code>

app.php:

<code class="php">$db = new Database();
$api = new MyAPI($db);
$user = $api->getUser($_POST['id']);</code>

This approach ensures that the database connection object is accessible within the MyAPI class, allowing you to execute queries and retrieve data successfully.

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