"Build" $_GET['xyz'] from variables

Question

I have two variables:

$method = "_GET";
$var = "id";

I now need this:

$parameter = $_GET['id'];

I tried something like this:

$parameter = ${$method.'[\''.$var.'\']'};

But it doesn't work. Any ideas?

Answer 1

Try:

$data = $$method;
$parameter = $data[ $var ];

The following:

$method = '_GET';
$var = 'id';

$data = $$method;
print_r($data);
echo $data[ $var ];

Will output:

Array
(
    [id] => test
)
test

Assuming the query string is ?id=test

@Leggendario pointed out an interested caveat: This won't work outside of the global scope, even though $_GET is a super global. You have to add global $$method before you can reference $$method in a function.

Also, it turns out there is a one-liner that will do this:

${$method}[$var];

Answer 2

Since you're not concentrating any strings to form the variable name, just put it in {}:

$parameter = ${$method}[$var];

---

Another possible solution, since the only two methods are _GET and _POST, is to use a ternary operator instead:

$parameter = $method == "_GET" ? $_GET[$var] : $_POST[$var];

Answer 3

That's basically a variable-variable:

$method = '_GET';
$var = 'id';

$foo = $$method[$var];

Turns out to not work at all... Yay php consistency, and I've learned my new thing for today.

This works:

php > $_GET['id'] = 'foo';
php > $method = '_GET';
php > $offset = 'id';
php > echo ${$method}[$offset];
foo

and turns out to have been documented: http://php.net/manual/en/language.variables.variable.php search for "ambiguity"

Answer 4

You could try the following:

filter_input(constant("INPUT" . $method), $var);

The constant() function let's you reference the INPUT_GET constant value for the filter_input() function by string name.

Using this method, you are retrieving the value and have the option to filter/sanitize it using the filter values on this page for extra security all in one setup.