Run MySQL query from external script with Slim Framework - php

Question

I am using Slim Framework to create REST API.
There is also table in my mysql db where I store information about each request to server.
I have separate file called functions.php where I have log_request() function
require_once('dbconnect.php');
function log_request() {
global $mysqli;
$query = "INSERT INTO log_table (....) VALUES (...) ";
$mysqli->query($query);
}
If I run this script - new record is added to my table. But when I run it using Slim
$app->get('/api/something', function($request, $response) {
require_once('dbconnect.php');
include_once('functions.php');
log_request();
});
I am receiving this error
Call to a member function query() on null
So $mysqli inside log_request() is null - why does it happen?

Answer 1

Because $mysqli; is not in global scoped. You are employing bad practices all across. Refactor your code to take advantage of the advanced Slim PHP features such as Dependency Container or Dependency Injection.
By including the dbconnect file inside another function you have effectively scoped its variables to that block scope. You could simply remove the global keyword and the code should work.

Answer 2

As mentioned by Scriptonomy - in order to use MySQL or to prepare, manage, and inject application dependencies we should use dependency container.
https://www.slimframework.com/docs/v3/concepts/di.html
Step 1
create dependencies.php file
// DIC configuration
$container = $app->getContainer();
$container['db'] = function ($c) {
$host = "localhost";
$user = "user";
$pass = "password";
$db_name = "database_name";
$mysqli = new mysqli($host, $user, $pass, $db_name);
return $mysqli;
};
Step 2
add this code before $app->run();
// Set up dependencies
require __DIR__ . '/../app/dependencies.php';
Step 3
Now you can use mysql (or any other injection)
$app->post('foo', function ($request, $response, $args) {
$res = $this->db->query("SELECT * FROM `app_jobs`");
.......
});