PHP what does it mean when using this '$$var'?

Question

I am trying to learn php, and I saw this in a foreach loop what does it mean? I understand &$var which its a direct reference to the memory address of the object. But what does $$var means? what is it exactly?

This is the example.

    foreach($this->vars as $key => $value)
    {
        $$key = $value;
        echo "$$Key: " . $$key;
        echo "Key: " . $key;
        echo "<br/>";
        echo "Value: " . $value;
    }

It is a [variable variable](http://php.net/manual/en/language.variables.variable.php). — Lix, Oct 07 '13 at 15:50
There are tutorials that cover this topic, this shouldn't be asked on SO, especially since the answer is available online from plenty of sources. — Mark, Oct 07 '13 at 15:51
@downvoters Lay off the down votes, use your close votes, this is what they're for. — user229044, Oct 07 '13 at 15:52
Use [SymbolHound](http://symbolhound.com/?q=what+is+%24%24var+php) for such search queries. — Amal Murali, Oct 07 '13 at 15:54
Ahh I get it thanks... although I couldn't FIND it in the internet, because I didnt know how to put the question in GOOGLE. Like "WHAT IS $$var in php"... didn't give me anything as actual answer, so thats why I aksed in SO. The wierd thing about that code in a template is why would I have variable variables? what would they be used for? Well thanks anyways. — S.H., Oct 07 '13 at 15:57
@Amal Murali: I did. He said "I understand &$var. But what does $$var means?" Not a reference that's for sure. :) — AbraCadaver, Oct 07 '13 at 21:26
@AbraCadaver: *Please* read [this](http://stackoverflow.com/questions/3737139/reference-what-does-this-symbol-mean-in-php) question. It's not about PHP reference. Reference as in mention/citiation. — Amal Murali, Oct 07 '13 at 21:30

Brad Christie · Accepted Answer · 2013-10-07T15:58:11.900

5

You're looking at a variable variable. e.g.

// original variable named 'foo'
$foo = "bar";

// reference $foo dynamically by evaluating $x
$x = "foo";
echo $$x; // "bar";
echo ${$x}; // "bar" as well but the {} allows you to perform concatenation

// different version of {} to show a more "complex" operation
$y = "fo";
$z = "o";
echo ${$y . $z}; // "bar" also ("fo" . "o" = "foo")

To show an example more closely matching your question:

$foo = "foo";
$bar = "bar";
$baz = "baz";

$ary = array('foo' => 'FOO','bar' => 'BAR','baz' => 'BAZ');
foreach ($ary as $key => $value){
  $$key = $value;
}

// end result is:
// $foo = "FOO";
// $bar = "BAR";
// $baz = "BAZ";

edited Oct 07 '13 at 15:58

answered Oct 07 '13 at 15:51

Brad Christie

100,477
16
156
200

OMG this is perfect... so the idea is to create ACTUAL variables from the indexes of the array GOD DAM. thats an A+ HeadShot to the answer. – S.H. Oct 07 '13 at 15:59
extract() does this without the loop and craziness. – AbraCadaver Oct 07 '13 at 16:45
@AbraCadaver: That's when you should read [why is it a bad idea to use `extract()`](http://stackoverflow.com/questions/829407/) :) – Amal Murali Oct 07 '13 at 21:33
lol good response. But i did look into thank you anyways @AbraCadaver – S.H. Oct 07 '13 at 21:36
@Amal Murali: Blame the use not the tool. I'm not a novice. I state that it is roughly the same without the loop. – AbraCadaver Oct 08 '13 at 12:32

score 2 · Answer 2 · edited Jun 13 '18 at 15:29

2

It's a variable with the name $key. For example, If $k='somevar', then $$k = $somevar.

edited Jun 13 '18 at 15:29

AbraCadaver

78,200
7
66
87

answered Oct 07 '13 at 15:53

Sam Braslavskiy

1,268
10
19

AbraCadaver · Answer 3 · 2018-06-13T15:30:42.867

1

Variable variable. The var name is what is contained in $var.

If $key = 'test' then $$key will be evaluate to a var named $test.

Also, there are very few practical uses. Most often arrays would be better.

edited Jun 13 '18 at 15:30

answered Oct 07 '13 at 15:51

AbraCadaver

78,200
7
66
87

PHP what does it mean when using this '$$var'?

3 Answers3