How can the error of "Undefined variable: mysqli" and "Call to a member function query() on null" be resolved in the edit.php file in PHP?

The error "Undefined variable: mysqli" occurs when the mysqli object is not properly initialized in the edit.php file. To resolve this, make sure to include the database connection code at the beginning of the file to create the mysqli object. The error "Call to a member function query() on null" indicates that the mysqli object is not properly instantiated or there is an issue with the database connection. To fix this, ensure that the mysqli object is successfully created and connected to the database before executing any queries. 

<?php
include 'db_connection.php'; // Include the file containing the database connection code

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $id = $_POST['id'];
    $name = $_POST['name'];
    $description = $_POST['description'];
    
    // Check if mysqli object is properly initialized
    if ($mysqli) {
        $query = "UPDATE products SET name='$name', description='$description' WHERE id=$id";
        $result = $mysqli->query($query);
        
        if ($result) {
            echo "Record updated successfully";
        } else {
            echo "Error updating record: " . $mysqli->error;
        }
    } else {
        echo "Database connection error";
    }
}
?>

Keywords

PHP mysqli undefined variable call to a member function query()

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