$function() and $$variable

Question

What the heck is $function(); and $$variable for?

Have never heard of these before, and searching on google doesn't give anything useful (possible that my keywords aren't perfect).

via https://stackoverflow.com/questions/4891301/top-bad-practices-in-php/4891422#4891422

salathe · Accepted Answer · 2011-02-03 22:37:48Z

13

$function() is a variable function and $$variable is a variable variable.

Those linked pages should give you plenty to go on, or at the very least some actual words to search with.

edited Feb 3, 2011 at 22:37

answered Feb 3, 2011 at 21:23

salathe

52.1k12 gold badges108 silver badges134 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

jeroen · Accepted Answer · 2011-02-03 21:50:50Z

5

$$variable ~~can be quite useful. What it~~ does:

$a = 1;
$b = "a";
echo $$b;

Outputs 1

edited Feb 3, 2011 at 21:50

answered Feb 3, 2011 at 21:23

jeroen

91.8k22 gold badges117 silver badges132 bronze badges

6 Comments

ircmaxell Over a year ago

I've never seen a use for $$ that wasn't an outright abuse. Variable functions, ok. But straight variable variables (with double $$), never. Please prove me wrong with how useful they can be in good code...

jeroen Over a year ago

@ircmaxell I wanted to add an example, but I can´t seem to think of any :-) Where I have used a similar construction was when generating a new object where the type / class depended on a variable (all sub-classes of a main class), something like $product = new $type($some_var) where $type is the kind of product I wanted to create. I guess that´s similar.

ircmaxell Over a year ago

It's similar and acceptable to do that. But I've just never see $$ where it's not an example of what to do. I'd love to be proven wrong, but we'll see...

jeroen Over a year ago

@ircmaxell You are probably right, it seems the only time they come up is when people want to know what they do...

unsynchronized Over a year ago

@ircmaxell - that's a bit like saying arrays are not needed. why use $mydata["price"] and my $data["name"] when we can use $mydata_price and $mydata_name, or (another example) why use $filename[1] and $filename[2], when $filename_1 and $filename_2 works just as easily. in other words, indirection is one of the most basic principles in a programming language. it gives you the ability to do something with a value with caring what that value is for.

|

Collectives™ on Stack Overflow

$function() and $$variable

2 Answers 2

Comments

6 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

6 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related