Undefined variable - but it's right there

Question

Possible Duplicate:
Using global vars within a function in PHP the way you do it in Javascript

For some reason, the following program is giving me an error:

<?php
    $a = 1;

    function func() {
        echo $a;
    }

    func();
?>

That is the entire program. The error is:

Notice: Undefined variable: a in what.php on line 5

Am I misunderstanding something fundamental?

I find it interesting that the first Google result for "global variables php" http://php.net/manual/en/language.variables.scope.php starts with an example that is remarkably similar to your code. — Russell Borogove, May 30 '12 at 00:35
Bottom line: The function is written to utilize `$a` as a global variable, despite how furious the SO community is about "globals being evil". I highly doubt this is the entire logic behind the OP's application, and using a global variable solves the problem. — nickb, May 30 '12 at 00:39
@RussellBorogove - If he's new enough to programming how would he know to add the word "global" to his query? — Galen, May 30 '12 at 00:40
@Galen, he's got 29K rep and a bunch of 10+ answers to C/C++ programming questions under his belt. — Russell Borogove, May 30 '12 at 00:41
I've decided to make the variable a `static` local variable (I'm surprised to find that PHP has `static`) because it's an array and I'd like to avoid recreating it every time the function is called. — Seth Carnegie, May 30 '12 at 00:44

score 4 · Accepted Answer · answered May 30 '12 at 00:34

4

Due to variable scope $a is not available inside of the function. You need to pass it as an argument for func() to have access to it:

<?php
    $a = 1;

    function func($a) {
        echo $a;
    }

    func($a);
?>

answered May 30 '12 at 00:34

John Conde

What is the scope of `a` then? Are functions not closures in PHP? – Seth Carnegie May 30 '12 at 00:34
The only closures that exist in PHP are with their anonymous/lambda functions – Major Productions May 30 '12 at 00:39
@SethCarnegie PHP is not Javascript but it does (recently) have lambda functions with multiple ways of getting access to variables from different scopes. – Okonomiyaki3000 May 30 '12 at 00:53

score 2 · Answer 2 · answered May 30 '12 at 00:39

2

If you'd like to reference a global variable, you'll need to make use of the global keyword:

<?php
    $a = 1;

    function func() {
        global $a;

        echo $a;
    }

    func();
?>

answered May 30 '12 at 00:39

1

Despite being recommended against, this is still correct. I won't downvote it, but I'm certain that others will. :-P – ghoti May 30 '12 at 00:40
Anybody that downvotes this is just regurgitating whatever "best practice" they read on the Internet and claiming to have some inherent wisdom behind the language. While there are plenty of use-cases of when **not** to use global variables, in the scope and simplicity of this question, this answer is perfectly viable. Hence, +1. – nickb May 30 '12 at 00:42
@ghoti: These days, using globals is recommended against in pretty much every imperative language I can think of. But they also exist in pretty much every imperative language, so there must still be legitimate uses for them. – Ken Wayne VanderLinde May 30 '12 at 00:45

2 Answers2