Understanding global variables and how to define them, change them ...

[adrianTNT]

Hello.

 

I have a variable called $comments_per_page that is inside settings.php, ($comments_per_page = 10);

Then a main file comments.php that contains:

<?php
// include settings.php that contains the value of $comments_per_page
require settings.php;

function some_function(){
// I need to use $comments_per_page here (inside a function)
}
// I also need to use $comments_per_page here (outside of the function)
?>

 

I dont know how to access and use the variable $comments_per_page when inside or outside of a function, I know about 2 things but I am not sure how to use them:

$GLOBALS['comments_per_page'];

global $comments_per_page;

 

- Which one of these 2 ^ I need to use inside and outside of a function when accessing and modifying $comments_per_page variable?

- When I just have "$comments_per_page = 10" inside settings.php does that mean it was created as a global variable?

 

Thank you.

- Adrian.

[Balmung-San]

Inside the function you need to use global $comments_per_page; before using it. That way you use the global instead of the local.

 

Outside of the function I believe you can just use $comments_per_page.

 

However, if you wish to be exactly sure about it, you can use $GLOBALS['comments_per_page'].

[Jessica]

You might consider setting $comments as a constant instead. That automatically makes it global.

define('COMMENTS_PER_PAGE', 10);

 

then in the function use it

print COMMENTS_PER_PAGE;

 

If you want to be able to change it that won't work, but as you said it's a setting I figure a constant will work better.

[adrianTNT]

You might consider setting $comments as a constant instead. That automatically makes it global.

define('COMMENTS_PER_PAGE', 10);

then in the function use it

print COMMENTS_PER_PAGE;

If you want to be able to change it that won't work, but as you said it's a setting I figure a constant will work better.

Yes, it is a setting and making it constant as you said could work, but I have more variables to use in same script and I was trying to figure out the way I have to use the other ones too.

 

Inside the function you need to use global $comments_per_page; before using it. That way you use the global instead of the local.

Outside of the function I believe you can just use $comments_per_page.

However, if you wish to be exactly sure about it, you can use $GLOBALS['comments_per_page'].

so if inside a function I add

global $comments_per_page and after that I change it's value inside the same function does this mean the variable value is also changed globally? Or only temporary to be used inside that function?

 

[Balmung-San]

It will be changed globally.

[Jessica]

AFAIK: It will be changed globally because it is a global variable. You might want to read up on passing by reference also.

[adrianTNT]

It will be changed globally.

Thanks, you are right. (I should have made a quick test for that).

 

 

AFAIK: It will be changed globally because it is a global variable. You might want to read up on passing by reference also.

I am not familiar with this 'passing by reference' I seen it again today at http://www.php.net/global but I dont realy understand what it is, I am kind of new to php

I will try to use "global $variable_name" inside functions (now that I am sure what it does) and see if that fixes my issues.

 

Thank you.

[adrianTNT]

I got into an issue: when inside a function and use global $comments_per_page; I get:

 

Parse error: parse error, unexpected T_GLOBAL

 

Why could this happen ?

 

edit: sorry about that, it was because of something else.

[Jessica]

It's probably the line before that.