Is there any reason for using $$

[Razzeal]

I've been assigned to improve a piece of code but i've stumbled into a problem.
The code uses a variable called $$id, in the database this number should equal 640, 641, 642 etc
The variable is like this:

$id = "i" + $index (index is a number from 1 to 15)

and then in the query it says:

Where id =". $$id

I need to get the id and I need it to be something like 640 etc, but i don't know what i should do...

can anybody help me???

thx,

Razz

[hvle]

are you sure this is PHP?

[GingerRobot]

The use of $$ is using a variable variable. Its quite hard to explain why to use them and what they do...and i dont quite understand the use of them in your script either.

[kenrbnsn]

Yes, it's PHP. Using a double $ indicates that it is a variable variable. See http://w.php.net/manual/en/language.variables.variable.php for more information.

If the index needs to be a different number, use a different mechnism for setting it:
[code]<?php
$some_maximum = 999; // set this to the highest $id+1
for ($id = 640;$id < $some_maximum;$id++) {
//
//  do stuff
//
}?>[/code]

Ken

[ShogunWarrior]

It comes in handy for stuff like object properties like so:
[code]
//*Inside the class*
function setVar($i)
{
  $name = 'id' . strval($i);
  $this->$$name;
}

//Set property
$x->setVar(15);
[/code]

And now you can use [b]$x->id15[/b]

It would come in handy parsing data so you could refer to the data by properties like:
[b]$doc->xml->title[/b] etc. etc.

[Daniel0]

[quote author=kenrbnsn link=topic=100190.msg395097#msg395097 date=1152623923]Using a double $ indicates that it is a variable variable.[/quote]

Heh, didn't knew they were called that... quite a funny name