Millistele andmetüüpidele on keelatud määrata indeksväärtust?

In PHP, assigning an index value (for example, when accessing an array via square brackets) is prohibited for the following data types:

• Scalar types (int, float, string, bool) — they are not arrays or objects, so you cannot do something like $intVar[0] = 'a';.
• NULL — assigning an index is not allowed because NULL is not an array or an object.

Index assignment is only possible for:

• Arrays
• Objects implementing the ArrayAccess interface

Example:

$arr = [];
$arr[0] = 'value'; // correct

$intVar = 10;
$intVar[0] = 'a'; // error