PHP - Accessing variables from different files

Question

I have 3 files in my project. For arguments sake let's called them a.php, b.php and c.php.

In a.php I have a declared variable: $sql_connection

In b.php I have declared a function: check_if_logged_in()

With these declared, I now want to be able to use the variables across my files. I have included a.php in my b.php file, and I included my b.php inside c.php.

I'd expect this all to work but for some reason b.php isn't getting $sql_connection from a.php?

My a.php file:

<?php

    $sql_connection = mysqli_connect("localhost", "user", "password", "database");

?>

My b.php file:

<?php

    include ("a.php");

    function check_if_logged_in() {

        $sqlquery = mysqli_query($sql_connection, ...

    }

?>

My c.php file:

<?php

    include ("b.php");

    check_if_logged_in();

?>

Your files "communicate" properly but you have to learn about [variable scope](http://php.net/manual/en/language.variables.scope.php). And **no**, the `global` keyword is not the solution to your problems. It is the cause of other, bigger problems that lurk in the dark, waiting for you to use it. — axiac, Nov 07 '17 at 15:59
@axiac I mean by defintion it is an article...if found the answer within the article you provided so thank you for that. — A Friend, Nov 07 '17 at 16:10

Latheesan · Accepted Answer · 2017-11-07T16:11:32.607

2

The problem is you are trying to use the variable $sql_connection within a function, which is initialised/declared outside; i.e. you have a scope issue!

Read up on it here: http://php.net/manual/en/language.variables.scope.php

Solution;

A. Pass $sql_connection to the function call like this: check_if_logged_in($sql_connection)

or

B. Use the global for e.g.

function check_if_logged_in() {
    global $sql_connection;
    $sqlquery = mysqli_query($sql_connection, ...
}

P.S. Although option B works; it is not recommended as it is considered bad pratise; see Are global variables in PHP considered bad practice? If so, why?

edited Nov 07 '17 at 16:11

answered Nov 07 '17 at 16:02

Latheesan

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Using the `global` keyword is not recommended, and is considered bad practice. – GrumpyCrouton Nov 07 '17 at 16:08
Yes, I meant to mention that; forgot. Answer updated. – Latheesan Nov 07 '17 at 16:10

score 0 · Answer 2 · answered Nov 07 '17 at 16:02

0

You need to pass the params.

function check_if_logged_in($sql_connection) {
$sqlquery = mysqli_query($sql_connection, ...

So

check_if_logged_in($sql_connection);

answered Nov 07 '17 at 16:02

marcozipsp

49
3

I never said this at the time but you were correct and also deserved the correct answer badge. Thank you for contributing! – A Friend Dec 30 '19 at 23:35
Better late than never ahahah :) – marcozipsp Jan 13 '20 at 14:45

PHP - Accessing variables from different files

2 Answers2