Accessing global variables within functions in PHP

Question

There are multiple times in one page where I need to connect and subsequently query a MySQL database, yet my code won't let me. I think it might be something to do with how my files are nested but it makes no sense. I am opening the SQL connection in the header file. The top of the offending page looks like the following:

<?php 
$page_title = 'Dashboard';
include('templates/header.inc'); // includes a 'require_once('mysqli_connect.php') and a small query to the database;
require_once('includes/functions.php');
require_once('includes/dashboard_sql.php'); // Contains functions which connect to database (which are failing.)
?>

I get the PHP error

Notice: Undefined variable: dbc in /Library/WebServer/Documents/pediatory_site/includes/dashboard_sql.php

Where $dbc is the database connection defined in mysqli_connect.php.

If anyone could help me out that would be great.

Answer 1

It probably has to do with scope.

$dbc = 1;

function foo() {
   echo $dbc; // Undefined variable
   echo $GLOBALS['dbc']; // 1, like defined above
   $otherVar = 2;
}

echo $otherVar; // Undefined variable

If the $dbc variable is used multiple times, it's shorter to write:

function foo() {
   global $dbc;
   echo $dbc; // 1, like defined above
}

Answer 2

I think when using the Require_Once method for creating a db connection the var gets cleared after the method closes the connection to the file. Try require or include for this kind of operations, and check if that works

<?php 
$page_title = 'Dashboard';
include('templates/header.inc'); // includes a 'require_once('mysqli_connect.php') and a small query to the database;
require_once('includes/functions.php');
include('includes/dashboard_sql.php'); // Contains functions which connect to database (which are failing.)
?>

so, i changed the require_once into an include method in the code you posted, try and go to the templates/header.inc and change the require_once method to a include and check if that helps.

it should. otherwise try creating the connection to the database in the same file, instead seperetated connections over separate files.