I can't count results in my database with PDO - php

Question

I have this error has shown:
Notice: Undefined variable: conn in D:\xampp\htdocs\website\core\functions\users.php on line 4
Fatal error: Call to a member function query() on null in D:\xampp\htdocs\website\core\functions\users.php on line 4
this is connect database
connect.php
<?php
$servername = "localhost";
$user = "root";
$passwd = "";
$dbname = "userdata";
try {
$conn = new PDO("mysql:host=$servername;dbname=$dbname", $user, $passwd);
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $exc) {
die($exc->getMessage());
}
?>
and in this part I have the problem
users.php
<?php
function user_exists($username){
$sql ="SELECT COUNT('id') FROM users where username = '$username'";
$query = $conn->query($sql);
$result = $query->fetchAll(PDO::FETCH_ASSOC);
if(count($result)){
$res = 0;
}else {
$res = 1;
}
return $res;
}
?>
and this where I connected users.php with connect.php
init.php
<?php
session_start();
require 'database/connect.php';
require 'functions/users.php';
require 'functions/general.php';
$errors = array();
?>

Answer 1

This is a variable scope problem.
Because $conn is set / declared outside of your function, you do not have access to it inside of your function.
Modify your function as follows:
function user_exists($username){
// This gets you access to the $conn variable inside the function.
global $conn;
$sql ="SELECT COUNT('id') FROM users where username = '$username'";
$query = $conn->query($sql);
$result = $query->fetchAll(PDO::FETCH_ASSOC);
if(count($result)){
$res = 0;
}else {
$res = 1;
}
return $res;
}