The & operator?

[rheroux]

Okay, I'm looking through some of the invision board code and I'm simply trying to figure out how everything ties together.

Here's a small snippet from index.php:

function info() {
		global $sess, $std, $DB, $root_path, $INFO;

	$this->vars = &$INFO;

	$this->vars['TEAM_ICON_URL']   = $INFO['html_url'] . '/team_icons';
	$this->vars['AVATARS_URL']     = $INFO['html_url'] . '/avatars';
	$this->vars['EMOTICONS_URL']   = $INFO['html_url'] . '/emoticons';
	$this->vars['mime_img']        = $INFO['html_url'] . '/mime_types';

}

Here's what I think I know about it. It's declaring the five variables as global's that will be used later on.

Then it's taking the information from $INFO to configure the conf_global.php file correctly (ie the correct paths are being set.)

It's the $this->vars = &INFO that's stumping me. I'm not sure what the & operator's function is when it's prepended infront of a variable. Can someone enlighten me?

Thanks.

[samscripts]

It means that rather than just copying $INFO to $this->vars, $this->vars becomes the same as $INFO.

I'm not making much sense here, so for a somewhat more intelligible description, see this page in the manual:

http://www.php.net/manual/en/language.references.php

I think what that bit of code is doing is setting the values for $this->vars which will then also be set throughout the script for $INFO.

eg: $INFO['TEAM_ICON_URL'] will now be set to $INFO['html_url'] . '/team_icons', just as $this->vars['TEAM_ICON_URL'] is.

I think thats what its doing anyway,

Sam

[merkinmuffley]

http://www.php.net/manual/en/language.references.php

normally, assignment in php means "copy the variable content of this name into the variable content of another name." using the & changes it to mean "point this name to the same variable content that is also reference by that name." example:

// Some variable content named $a
$a = "Time flies like an arrow";
echo $a."<br>";

// Copy that content to a new name, $b
$b = $a;
echo $b."<br>";

// Make a reference to the same variable content
// under a new name, $c
$c =& $a;
echo $c."<br>";

// You can change the variable content by 
// changing either $a or $c
$a = substr($a, 5);
$c .= " covered in molasses";

echo $a."<br>".$c;

output:
Time flies like an arrow
Time flies like an arrow
Time flies like an arrow
flies like an arrow covered in molasses
flies like an arrow covered in molasses

[rheroux]

Thanks for the explanations guys.

I think I understand it now. Basically, in merkinmuffley's example, whatever changes I make to $c are made to $a, and vica versa since they are assigned by reference.

[mattmecham]

Hey! I recognise that 😉

I used a reference rather than a copy so that any changes made to $INFO in the scripts would be reflected in $ibforums->vars without the need to manually update the $ibforums object.