Reference is adding item to array

Question

I have the following method where you pass a list of items in, and the first item is what you want to see if it exists, and the following items are the path to the item.

In the following I have 2 print_r statements, one before the for and one after it.

public function exists(){
    $keys  = func_get_args();
    $value = array_shift($keys);

    $ref = &$_SESSION;
    print_r($_SESSION);
    for($x = 0; $x < sizeof($keys); $x++){
        $ref = &$ref[$keys[$x]];
    }
    print_r($_SESSION);
    if(!is_array($ref)){
        unset($ref);
        return false;
    }
    $found = in_array($value, $ref);
    unset($ref);
    return $found;
}

and when I call it like this:

$obj->exists(123, "cart");

I get these two arrays from those print_r's:

Array
(
    [id] => 1
    [email] => [email protected]
    [user] => TheColorRed
    [first] => Billy
    [last] => Bob
    [ZingLoggedIn] => 1
)
Array
(
    [id] => 1
    [email] => [email protected]
    [user] => TheColorRed
    [first] => Billy
    [last] => Bob
    [ZingLoggedIn] => 1
    [cart] => 
)

My question is, why is it adding cart to the array? It should only be checking to see if it exists.

Try to enable E_ALL error reporting level and check your logs first. PS: your unset is completely redundant there. — zerkms
– zerkms, Commented Jan 20, 2015 at 0:03
Interesting. Wouldn't an undefined offset notice be raised in the for loop? Maybe do an isset check and break if it returns false. — danronmoon
– danronmoon, Commented Jan 20, 2015 at 0:03
@zerkms I have error_reporting = E_ALL & ~E_DEPRECATED & ~E_STRICT and display_errors = On — Get Off My Lawn
– Get Off My Lawn, Commented Jan 20, 2015 at 0:11
@The Boogie Man: and you don't get notices/warnings for this code? — zerkms
– zerkms, Commented Jan 20, 2015 at 0:11

Ja͢ck · Accepted Answer · 2015-01-20 00:29:40Z

2

This is the side effect of using references on array elements; if the element doesn't exist it gets created. The unset() afterwards doesn't change that. Consider not using references; since you're only reading the values, there should be no copy-on-write taking place:

public function exists()
{
    $keys  = func_get_args();
    $value = array_shift($keys);

    $ref = $_SESSION;
    foreach ($keys as $key) {
        if (!isset($ref[$key])) {
            return false;
        }
        $ref = $ref[$key];
    }
    return is_array($ref) && in_array($value, $ref);
}

edited Jan 20, 2015 at 0:29

answered Jan 20, 2015 at 0:12

Ja͢ck

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7 Comments

Get Off My Lawn Over a year ago

will this work for $obj->exists("cat", "item1", "item2") -> $array['item1']['item2']?

zerkms Over a year ago

@The Boogie Man: what if you try before you ask?

Ja͢ck Over a year ago

@TheBoogieMan It won't create array elements; with a function called exists() I wouldn't expect that kind of side effect anyway.

zerkms Over a year ago

@Ja͢ck but why don't you use isset as well?

Get Off My Lawn Over a year ago

I added && array_key_exists($key, $ref) to the if statement because it was saying the index "cart" doesn't exist. Is it a good idea to add that?

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