Passing a db connection in function - php

Question

I have a database function and I am trying to figure out if passing the db info can be done in the same format as a new function
I was using a global db connect function but was told that is a bad practice so I wrote one of my functions as follows
function mysystem(mysqli $db){
//mystuff here
}
and it connects to the database with no issue.
my 2nd function is a little different I created a function to check if anything duplicate exists
function check_duplicate_entries($table, $column_name, $value){
$db = new mysqli(DB_HOST, DB_USERNAME, DB_PASSWORD, DB_NAME);
$stmt = $db->prepare("SELECT * FROM $table WHERE $column_name = ?");
$stmt->bind_param('s', $value);
$stmt->execute();
$result = $stmt->get_result();
$stmt->close();
if (mysqli_num_rows($result) == 1) {
return true;
} else {
return false;
}
}
is there a way that I can pass my db info like the rest of my functions instead of calling a new db connection.
like this
function check_duplicate_entries(mysqli $db, $table, $column_name, $value){

Answer 1

Yes. It's common practice to use singleton pattern to handle this. This is code example for PDO, you can refactor it to mysqli
class MysqlConnector
{
private static $connection;
private function __construct()
{
}
public static function getConnection(): PDO
{
$username = "root";
$password = "";
$database = "blog";
$servername = "localhost";
if (!empty(self::$connection)) {
return self::$connection;
}
self::$connection = new PDO("mysql:host=$servername;dbname=$database", $username, $password);
self::$connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
return self::$connection;
}
}
// now you can get your connection anywhere
// just make sure this class is available in your current namespace
$connection = MysqlConnector::getConnection();
$connection->query('SELECT COUNT(*) FROM articles');