CODEWITHSUNDEEP
phpreferenceunset
onassar
onassar

Reputation: 3568

unsetting php reference

So I have this function, and it returns me a reference to a particular point to the array passed in. I want to make a call to unset that will then remove the result from the array/reference, but calling unset only removes the reference, not the data from the original array. Any thoughts?

Upvotes: 2

Views: 1902

Answers (3)

outis
outis

Reputation: 77440

Note that the behavior of unset on references is by design. You could instead return the index of the element to remove, or an array of indices if the array isn't flat.

For example, you could use the following function:

function delItem(&$array, $indices) {
    $tmp =& $array;
    for ($i=0; $i < count($indices)-1; ++$i) {
        $key = $indices[$i];
        if (isset($tmp[$key])) {
            $tmp =& $tmp[$key];
        } else {
            return array_slice($indices, 0, $i+1);
        }
    }
    unset($tmp[$indices[$i]]);
    return False;
}

Or, if you prefer exceptions,

function delItem(&$array, $indices) {
    $tmp =& $array;
    while (count($indices) > 1) {
        $i = array_shift($indices);
        if (isset($tmp[$i])) {
            $tmp =& $tmp[$i];
        } else {
            throw new RangeException("Index '$i' doesn't exist in array.");
        }
    }
    unset($tmp[$indices[0]]);
}

Upvotes: 0

zombat
zombat

Reputation: 94217

Setting the reference to null will destroy the data that the reference (and any other reference) is linked to.

See Unsetting References in the manual for more on this. Basically you want to do the following (taken from the comments):

$a = 1;
$b =& $a;
$c =& $b;  //$a, $b, $c reference the same content '1'

$b = null; //All variables $a, $b or $c are unset

In your case, it'll look something like this:

$a =& getArrayReference($whatever);
$a = null;

EDIT

To clear up any misconceptions, here's what you get when you unset array references:

$arr = array('x','y','z');

$x =& $arr[1];
unset($x);
print_r($arr);
//gives Array ( [0] => x [1] => y [2] => z )

$x =& $arr[1];
$x = null;
print_r($arr);
//gives Array ( [0] => x [1] => [2] => z )

Notice how the second array index does not have it's content deleted in the first example with unset(), but the second example of setting the reference to null accomplishes this.

Note: If you need to unset the array index as well, which I'm a bit unclear on as to whether you do or not, then you'll need to find a way to reference the key of the array instead of the value, likely by altering the return value of your function.

Upvotes: 4

Rune Kaagaard
Rune Kaagaard

Reputation: 6798

It is expected behavior that unsetting a reference does not unset the variable being referenced. One solution is to return the key instead of the value, and using that to unset the original value.

Upvotes: 1

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