Using function to create a connection - php

Question

I'm trying to create a connection using function in my other php file. So I can access it in every php file. How can I call the function inside my class from another php file. What is the proper way creating instance of my function will I put it in the top of my file or inside my class? I try to run my system but the connection won't load.
connection.php
<?php
DEFINE ('host', 'localhost');
DEFINE ('username', 'root');
DEFINE ('password', '');
DEFINE ('database', 'librarysystem');
function getConnection()
{
$myDB = mysqli_connect(host,username,password,database);
if (!$myDB)
{
trigger_error ('Could not connect to MySQL: ' . mysqli_connect_error());
}
else
{
return $myDB;
}
}
?>
Another file where I'm gonna call my function or method.
loginCRUD.php
<?php
error_reporting(0);
require_once ('../connection/connection.php');
$myConnection = getConnection();
class loginCRUD
{
public function readLogin($dbusername,$dbpassword)
{
$statement = $myConnection->prepare("SELECT * FROM loginmodule WHERE loginUsername = ? AND loginPassword = ? LIMIT 1");
$statement->bind_param("ss", $dbusername, $dbpassword);
if($statement->execute())
{
$result = $statement->get_result();
if($result->num_rows)
{
$row = $result->fetch_assoc();
return $row;
}
else
{
return false;
}
}
else
{
return false;
}
}
}
(new loginCRUD)->readLogin($dbusername,$dbpassword);
?>

Answer 1

There can be at least two possible ways of passing $myConnection to your loginCRUD class.
First is to create $myConnection in a class itself:
class loginCRUD
{
protected $dbCon;
public function __construct()
{
$this->dbCon = getConnection();
}
public function readLogin($dbusername,$dbpassword)
{
$statement = $this->dbCon->prepare("YOUR SQL")
// other codes
}
}
(new loginCRUD)->readLogin($dbusername,$dbpassword);
Second is to pass $myConnection as an argument to your class constructor:
class loginCRUD
{
protected $dbCon;
public function __construct($myCon)
{
$this->dbCon = $myCon;
}
public function readLogin($dbusername,$dbpassword)
{
$statement = $this->dbCon->prepare("YOUR SQL")
// other codes
}
}
$myConnection = getConnection();
(new loginCRUD($myConnection))->readLogin($dbusername,$dbpassword);

Answer 2

The reason you are getting an error is due to your variable scope. In your loginCRUDclass you try to access a variable called myConnection, it fails to find it because the scope of the function is only that function. It doesn't know that you mean the global declared variable. A correct way of fixing this should be:
...
public function readLogin($dbusername,$dbpassword)
{
global $myConnection;
$statement = $myConnection->prepare("SELECT * FROM loginmodule WHERE loginUsername = ? AND loginPassword = ? LIMIT 1");
$statement->bind_param("ss", $dbusername, $dbpassword);
if($statement->execute())
{
...
For reference: Accessing variables and methods outside of class definitions