PHP using variable value in a variable name

Question

I have some variables like this:

$barbarian = 7;
$archer = 7;
$giant = 7;

And a function like this:

function army($troopData,$troop,$thing){

    if(isset($troop) && $troopData+1 == ${"$thing"}){
        $troopData++;
        $text = "<span class='army-icon active top-lvl $thing-icon'><span>$troopData</span></span>";
    }elseif(isset($troop)){
        $troopData++;
        $text = "<span class='army-icon active $thing-icon'><span>$troopData</span></span>";
    }else{
        $text = "<span class='army-icon $thing-icon'><span></span></span>";
    }
  return $text;

}

Notice the first if: if(isset($troop) && $troopData+1 == ${"$thing"}){

The function is called like this: army($troopslvl4000000,$troops4000000, "barbarian"); army($troopslvl4000001,$troops4000001, "archer");

The last parameter is named $thing in the function.

So I need to first line of the if to check if:

1) $troop is set. 2) $troopData+1 == $barbarian (or whatever thing is. $archer for the second function call)

But it isn't working. It is always using the elseif or the else. The first if never gets called...

In your first if statement, what is this ${"$thing"} supposed to be? That doesn't look like valid PHP to me — mituw16
– mituw16, Commented Aug 21, 2015 at 14:41
@mituw16 that is variable variablename. if $varname = archer and $archer = 5 then $$varname = 5 — inetphantom
– inetphantom, Commented Aug 21, 2015 at 14:49
yeah, the ${"$thing"} notation is also correct, as is $$thing. I think the issue is the lack of the global statements as in my answer. — Marten Koetsier
– Marten Koetsier, Commented Aug 21, 2015 at 14:52
Note that with variable variablenames you have some magic behaviour. I would try to avoid such magical stuff for readability of the code. — inetphantom
– inetphantom, Commented Aug 21, 2015 at 14:58
Interesting. In all my years doing PHP, I've never come across ${"$variable"} syntax before. Thanks for the explanation! — mituw16
– mituw16, Commented Aug 21, 2015 at 16:04

Marten Koetsier · Accepted Answer · 2015-08-21 14:43:27Z

1

You could use a construct like:

$s1 = "somevar";
$$s1 = "test";
echo $somevar; // will output: test

This in your code:

function army($troopData,$troop,$thing){
    global $barbarian;
    global $archer;
    global $giant;

    if(isset($troop) && $troopData+1 == $$thing){
    ...
}

Edit:

note that you should enable access to the $barbarian etc. variables inside the function!

answered Aug 21, 2015 at 14:43

Marten Koetsier

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1 Comment

inetphantom Over a year ago

In the EditCase you should get a warninng from php which says "$barbarian is not defined, assumed 'barbarian' " or something like this

inetphantom · Accepted Answer · 2015-08-21 14:52:30Z

0

For readability to avoid mistakes with the priority of oporaters add brackets like

if(isset($troop) && ( $troopData+1 == ${"$thing"})

In this case as a comment said you do not have to: http://php.net/manual/fa/language.operators.precedence.php

edited Aug 21, 2015 at 14:52

answered Aug 21, 2015 at 14:41

inetphantom

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2 Comments

Marten Koetsier Over a year ago

== has higher preceedence than &&, so leaving the parentheses out is safe. However, sometimes readability improves if you do use the superfluous parentheses...

inetphantom Over a year ago

@MartenKoetsier changed that. Sory!

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