mysqli and global variable - php

Question

I've been been on this for hours trying to find the small mistake I've done and I just can't find it... All I'm doing is calling a variable as global in a function and it's just not working even though it worked fine with the function above it...
I get an error saying mysqli is null...
include 'data/mysqli_connect.php';
function process_login(){
global $mysqli;
$username = $_SESSION['username'];
$sql = "SELECT * FROM auth WHERE user='".mysqli_real_escape_string($mysqli,$username)."'";
$query = mysqli_query($mysqli,$sql);
if(mysqli_num_rows($query)>0){
$sql = "DELETE FROM auth WHERE user='".mysqli_real_escape_string($mysqli,$username)."'";
$query = mysqli_query($mysqli,$sql);
if(!$query){
die(mysqli_error());
}
}
$sql = "INSERT INTO auth (user, session) VALUES ('".mysqli_real_escape_string($mysqli,$username)."', '".$_SESSION['id']."')";
$query = mysqli_query($mysqli,$sql);
if(!$query){
echo "Can not insert info into database!<br />". mysqli_error();
}else{
header("Location:chat.php");
}
}
function logout(){
global $mysqli;
$sql = "DELETE FROM auth WHERE session='".mysqli_real_escape_string($mysqli,$_SESSION['id']). "'";
$query = mysqli_query($mysqli,$sql);
if(!$query){
echo "Can not delete info from database!";
}else{
session_destroy();
header("Location: chat.php");
}
}
function get_username(){
global $mysqli;
$sql = "SELECT * FROM auth WHERE session='".mysqli_real_escape_string($mysqli,$_SESSION['id']). "'";
$query = mysqli_query($mysqli,$sql);
$row = mysqli_fetch_array($query);
if(mysqli_num_rows($query) == "0"){
$username = "Guest";
}else{
$username = $row['user'];
}
return $username;
}
function post_message(){
global $mysqli;
$text = addslashes(htmlentities(htmlspecialchars($_REQUEST['text'])));
$sql = "INSERT INTO chat (time, user, text) VALUES ('".date("H:i")."', '".get_username()."', '".$text."')";
$query = mysqli_query($mysqli,$sql);
if(!$query){
die(mysqli_error());
}
}
mysqli_connect.php
$mysqli = mysqli_connect(localhost, "info", "info", "info");
Like I said it worked on the function above this one but not this one, it doesn't make sens... I'm guessing I have a stupid mistake in there somewhere just don't know where.
By the way,the functions that I tested and work are process_login() and logout() and get_username()
get_username() runs first then process_login(). post_message() runs from a jquery code that calls it when i press on enter that probably works fine since i can see the error code when i press enter.
Oh and sorry about the bad code formatting,not sure how to fix it on here.
Thank you for any help or advice you may find.

Answer 1

How/When is post_message() called? From what you edited in, I can't find anything specifically in that that would clear the $mysqli variable - but to debug it, we would need more of the program flow.
Or you could create a 'hack' in the code and within post_message() after you declare global $mysqli;, do include 'data/mysqli_connect.php'; again since the $mysqli reference to your DB connection has been lost by then. But, ideally, you need to follow the flow of your code to figure out where to fix it correctly - and your flow seems not to be able to be posted fully, or is too great to post fully here.
(Too long for a comment, so this response comes in answer form, my apologies.)

Answer 2

Instead of making $mysqli a global variable, try passing it as an additional parameter to your functions. I was having the same problem and that's how i solved it. ie...
function post_message($mysqli){
$text = addslashes(htmlentities(htmlspecialchars($_REQUEST['text'])));
$sql = "INSERT INTO chat (time, user, text) VALUES ('".date("H:i")."',
'".get_username()."', '".$text."')";
$query = mysqli_query($mysqli,$sql);
if(!$query){
die(mysqli_error());
}
Hope this works for you.