How to pass connection varible in other php document - php

Question

Help me with this code: I get this error.
Notice: Undefined variable: dbCon in C:\xampp\htdocs\Project\core\functions\general.php on line 5
Warning: mysqli_real_escape_string() expects parameter 1 to be mysqli, null given in C:\xampp\htdocs\Project\core\functions\general.php on line 5
Notice: Undefined variable: dbCon in C:\xampp\htdocs\Project\core\functions\Users.php on line 5
Warning: mysqli_query() expects parameter 1 to be mysqli, null given in C:\xampp\htdocs\Project\core\functions\Users.php on line 5
Fatal error: Uncaught Error: Call to undefined function mysqli_result() in C:\xampp\htdocs\Project\core\functions\Users.php:8 Stack trace: #0 C:\xampp\htdocs\Project\login.php(4): user_exists(NULL) #1 {main} thrown in C:\xampp\htdocs\Project\core\functions\Users.php on line 8
Main folder(name -> PHP) has Index.php:
<?php
include 'core/init.php';
include 'includes/overall/header.php';
?>
PHP folder has Login.php:
<?php
include 'core/init.php';
if(user_exists('sudin') === true)
{
echo 'exists';
}
?>
under php/core folder init.php:
<?php
session_start();
require 'database/connect.php';
require 'functions/general.php';
require 'functions/users.php';
?>
under php/core/database connect.php:
<?php
$dbCon=mysqli_connect('localhost','root','','project_point');
?>
under php/core/functions Users.php:
<?php
function user_exists($username)
{
$username = sanitize($username);
$query = mysqli_query($dbCon,"SELECT COUNT('Login_ID')FROM 'login' WHERE 'Username' = '$username'");
return(mysqli_result($query,0)==1) ? true : false;
}
?>
under php/core/functions general.php:
<?php
function sanitize($data)
{
return mysqli_real_escape_string($dbCon,$data);
}
?>[enter image description here][1]
Sorry for the messy way, here is the treeview:
Thankful for the help

Answer 1

There are a few things wrong here.
Firstly, you have a variable scope issue and you're also using the wrong identifier qualifiers in your query being regular quotes:
So, remove the quotes for this:
SELECT COUNT('Login_ID')FROM 'login' WHERE 'Username'
^ ^ ^ ^ ^ ^ Remove those
or use ticks:
SELECT COUNT(`Login_ID`) FROM `login` WHERE `Username`
Checking for errors on it using mysqli_error($dbCon) http://php.net/manual/en/mysqli.error.php would have thrown you something about it once it would have fired.
Make your connection global in your user_exists() function
global $dbCon;
Read up on both:
Identifier qualifiers http://dev.mysql.com/doc/en/identifier-qualifiers.html
Variable scope http://php.net/manual/en/language.variables.scope.php

Answer 2

The connection variable is not defined in the function scope. The hotfix is to add it with the "global" construct.
function user_exists($username)
{
global $dbCon;
...

Answer 3

you are trying to use a local variable $dbCon inside the function user_exists.
you can just change that variable to be global
ex:
under php/core/database connect.php:
<?php
global $dbCon;
$dbCon=mysqli_connect('localhost','root','','project_point');
?>
under php/core/functions Users.php:
<?php
function user_exists($username)
{
global $dbCon;
$username = sanitize($username);
$query = mysqli_query($dbCon,"SELECT COUNT('Login_ID')FROM 'login' WHERE 'Username' = '$username'");
return(mysqli_result($query,0)==1) ? true : false;
}
?>

Answer 4

The issue is that $dbCon is not defined in the scope of any function.
You could do 3 things:
function user_exists($username){
$query = mysqli_query($GLOBALS['dbCon'] ...
function user_exists($username){
global $dbCon;
$query = mysqli_query($dbCon ...
However, using globals in functions like this is usually a bad coding style.
I would recommend doing something like the following:
function getconn(){
static $conn;
if(!isset($conn)){
$conn = new mysqli_connect(...);
}
return $conn;
}
function user_exists($username){
$query = mysqli_query(getconn() ...
I was just about to add the issues with your SQL syntax, but Fred beat me to it. I think you want backticks ` instead, not '.