hidden_array_element.md

Hidden array elements

Note: This has been fixed in PHP 7.2.0.

With hidden array elements I mean array elements you can't access anymore. They will be still displayed using debugging functions like var_dump.

Short description

On creating object properties with numeric names and casting such an object into an array the numeric object properties are hidden array elements.

Long description

In PHP you can cast an object into an array. (See http://www.php.net/manual/language.types.array.php#language.types.array.casting)

If an object is converted to an array, the result is an array whose elements are the object's properties. The keys are the member variable names.

Normally object propertie names can't be numeric because something like $obj->123 isn't valid. But if you use dynmaic object property notation like $obj->{123} it's possible.

Now if you cast such an object into an array the key becomes the numeric property name as a string and because numeric array keys will be converted into integers you can't acces such numeric strings.

PS: Object properties will be strings even if you create it as an integer.

Example:

(http://3v4l.org/6uFqf)

$obj = new stdClass();
$obj->{123}   = "foo";
$obj->{'456'} = "bar";

$arr = (array)$obj;

var_dump($arr);
var_dump($arr['123'], $arr[123]);
var_dump($arr['456'], $arr[456]);

array(2) {
    ["123"] => string(3) "foo"
    ["456"] => string(3) "bar"
}

Notice: Undefined offset: 123 in ... on line 10
Notice: Undefined offset: 123 in ... on line 10
NULL
NULL

Notice: Undefined offset: 456 in ... on line 11
Notice: Undefined offset: 456 in ... on line 11
NULL
NULL