Can't use php variable from another file [duplicate] - php

Question

This question already has answers here:
Reference: What is variable scope, which variables are accessible from where and what are "undefined variable" errors?
(3 answers)
Closed 4 years ago.
like my title says, whenever I try to use my variables from another php file, it doesn't work (Undefined variable).
I did declare them in the file that I'm including.
For example, I have this file called variables.php that have this in it:
<?php
$DEBUG = TRUE;
$mysqli = new mysqli("127.0.0.1", "root", "", "29185917-database");
$DEBUG_LOG_FILE = "../log";
?>
And then I have another file called debug.php that tries to use the variable 'DEBUG' but it cannot access it. Here is my debug.php file:
<?php
require_once 'variables.php';
function echo_debug(string $message)
{
if($DEBUG) {
echo $message;
}
}
?>
Whenever I try to use my function echo_debug I get the error message :
Undefined variable 'DEBUG'.
Any help on this problem is appreciated :).

Answer 1

Functions have their own scope. The variable is accessible, just not from inside the function.
You could pass $DEBUG as a parameter
function echo_debug(string $message, bool $DEBUG)
Then you would call it as
echo_debug("comment that will help me debug in dev mode", $DEBUG);
Another option is to declare DEBUG as a constant,
define('DEBUG', true);
$mysqli = new mysqli("127.0.0.1", "root", "", "29185917-database");
$DEBUG_LOG_FILE = "../log";
Then, in your function you would check for that constant:
function echo_debug(string $message) {
if(DEBUG) { ... }
}
You could also use the global keyword, right above your if(), try to add global $DEBUG;.
require_once 'variables.php';
function echo_debug(string $message)
{
global $DEBUG;
if($DEBUG) { ... }
}
But generally the other two solutions are better, global variables are sometimes frowned upon.

Answer 2

As per my comment, you can also use a constant and avoid the variable issue altogether.
<?php
define('DEBUG', true);
$mysqli = new mysqli("127.0.0.1", "root", "", "29185917-database");
$DEBUG_LOG_FILE = "../log";
?>
Then in the function check if the constant has been defined
<?php
require_once 'variables.php';
function echo_debug(string $message) {
if (defined('DEBUG') && DEBUG === true) {
echo $message;
}
}
?>

Answer 3

do like this:
function echo_debug(string $message,$data)
{
if($data === TRUE) {
echo $message;
}
}
call function:
require_once 'variables.php';
$message = "comment that will help me debug in dev mode";
$output = echo_debug($message,$DEBUG);
print_r($output);