从多维$ _GET数组中获取已知键

Question

I want to create a function (or method) that can fetch any key from $_GET array (or a $_POST or $_COOKIE array). The $_GET array can be flat, non-existing or multi-dimensional. The keys are associative and they may not always exist - as when an empty form is submitted -> no $_GET parameter is set in the url.

Here is a sample url for the scenario that I want to support: http://www.example.com/foo?foo[name]=John&foo[color][]=red&foo[color][]=green&foo[color][]=yellow&foo[gender]=male.

The contents of this url shall be captured by the same get() function:

get($foo[name])  // Return value set in input field.
get($foo[color]) // Return array with none/one/many values (set in checkbox or multi-select, see sample code below).

// The functions shall be similar to:
$_GET['foo']['name'] // string
$_GET['foo']['color'] // array

The main use case in which I will be using the function is when a form is submitted, such as the one below. When the form is submitted, I want to fetch data from the checkboxes and radio buttons weather they are set or not.

<form method="GET">
<input type="text" name="foo[name]" value="">
<input type="radio" name="foo[gender]" value="male">
<input type="radio" name="foo[gender]" value="female">
</form>

Sample output for the form comes here.

Example 1: Form is posted with all fields set:

Array (
    [foo] => Array (
            [name] => John
            [color] => Array (
                    [0] => red
                    [1] => green
                    [2] => yellow
                )
            [gender] => male
        )
)

Example 2: Form is submitted as empty (so no keys exists, it is important that the function supports this scenario):

Array ()

Things I tried:

The first two scenarios with a flat or non-existing array are easy to manage, as shown in below function that will handle both flat and non-existing array keys. However, the function does not support multi-dimensional arrays (say, with up to two dimension levels).

// This will only work for a form that returns a flat $_GET array (e.g., http://www.example.com/foo?a=1&c=3). 
// `get('foo[color]')` will not do the trick.
function get($key) {
    if (isset($_GET[$key])) {
        return $_GET[$key];
    }
}

My question is how I can build a similar function that also supports a scenario with multi-dimensional arrays? How can I create the function so it will be valid for a multi-dimensional array?

Thanks.. :-)

PS: If your answer involves something like RecursiveArrayIterator(), I would appreciate a full example as this can be challenging to work with.

PPS: To reviewers who are quick on the dupe button: I am aware that StackOverflow has a ton of question regarding $_GET and arrays, and therefore encourage my reviewers to read and re-read the question before marking it as a duplicate. Again, the scenario here is how to create a function that supports getting a known key from a $_GET array, the $_GET array is multi-dimensional and it may or may not be set.

Answer 1

I have a feeling there's a cleverer way; and maybe I misunderstand the question.

<?php
$_GET = ['foo'=>[ // just for this example, don't fiddle with _GET like this in production code....
    'name'=>'John',
    'colors'=>[
        'primary'=>['red','green','yellow'],
        'secondary'=>['white','purple']
    ],
    'gender'=>'male'
]];



echo '1 ', get('foo', 'name'), "
";
echo '2 ', var_export( get('foo', 'color'), true ), "
";
echo '3 ', var_export( get('foo', 'colors'), true ), "
";
echo '4 ', get('foo', 'colors', 'primary', 0), "
";
echo '5 ', get('foo', 'colors', 'secondary', 1), "
";
echo '6 ', get('foo', 'gender'), "
";


// see http://docs.php.net//functions.arguments#functions.variable-arg-list
function get(...$keys) {
    $cur = $_GET;
    foreach( $keys as $k ) {
        if ( !isset($cur[$k]) ) {
            return FALSE;
        }
        else {
            $cur = $cur[$k];
        }
    }
    return $cur;
}

prints

1 John
2 false
3 array (
  'primary' => 
  array (
    0 => 'red',
    1 => 'green',
    2 => 'yellow',
  ),
  'secondary' => 
  array (
    0 => 'white',
    1 => 'purple',
  ),
)
4 red
5 purple
6 male