Beware - PHP newcomers !

If, like me, you come to PHP from a background in C, there is
a big tripwire waiting to floor you !
-
If you declare a variable global in PHP, that
variable will NOT be available to your functions.
-
This had me in knots for hours yesterday and I just hope this post
can save any other newbies from tearing out their hair trying to
figure what happens. You always have to pass values to functions in
PHP as parameters.

-
Chris

 

lol nice post, i suffered the same fate a long time ago, makes me feel nostalgic

 

Interesting thing is, it seems to constrain one to write
better code !
-
It makes some parameter lists a bit lengthy but, when you
read through the script, the localisation is more clearly seen
which, I guess, means lower maintenance three months down
the line ........
-


-
Chris

 

yep, global vars are not my thing anyways

 

global are meant to declared inside the function, not outside

 

Yes, global is defined inside the function which allows the function to access the variable.

 

Chris:

As a newcomer, let me suggest to you that php.net is great for documentation... eg. http://php.net/global for how to access / use global variables.

 

Or you could use globals...

$myvar = "hi";

function printVar() {
  echo $GLOBALS["myvar"];
}

PHP:

 

Global variables are not really advisable. And if you do use them, don't declare them outside of a PHP function. Declare them INSIDE your PHP function.

If you're going to want values that can be accessed site wide, but not changed, use constants.
DEFINE('CONSTANT_NAME','CONSTANT_VALUE');

That way they can be accessed site wide and don't have to be declared more than once. Just make sure you include a config file or something that contains your constants when needing them.

 

In PHP, that is

I really want to know the deal with global variables (using global $var inside your function). Everyone seems to hate it, but from what I can tell it does not slow the script down, and it is definitely not insecure. So if someone could enlighten me?

 

well, like it was said before - you can access any variable as $GLOBALS['varname'] anyway. i guess a local global $varname is simply performing an extract() on $GLOBALS for that key to make it easier to access... but it also means changes applied to the variable during the function will keep when it returns. i cannot comment on memory usage but you can do tests:

function Bollocks() {
    echo memory_get_usage() . "<br />" . substr($GLOBALS['a'], 0, 20);
}

Bollocks();
$a = str_repeat("Hello", 5000);
Bollocks();

PHP:

this outputs memory usage for before and after $a is defined, when using the GLOBALS array:
100200 // before
125376 // after
HelloHelloHelloHello

when decalared as global $a:

    global $a;
    echo memory_get_usage() . "<br />" . substr($a, 0, 20);

PHP:

100416 // before is already higher by 216 bytes, just because...?
125688 // 312 bytes more allocated.
HelloHelloHelloHello

interesting. hrm...

 

Cool, thanks.