How does the “Array dereferencing” work on a scalar value of type boolean/integer/float/string as of PHP version 7.2.0?

Question

I am using PHP 7.2. I come across the following note from the arrays chapter of PHP Manual

Array dereferencing a scalar value which is not a string s

Answer 1

They are referring to non-complex types such as int or float.

In your example you are using an array. So you don't see the issue.

<?php
function getArray() {
    return array(1, 2222, 3);
}
$secondElement = getArray()[1]; // 2222

$null = $secondElement[123456]; // 123456 can be any number or string
var_dump($null);

// similarly:
$also_null = getArray()[1][45678];
var_dump($also_null);

The first pair of brackets is array-dereferencing on the array (1, 2222, 3), the second is array-dereferencing on an integer (2222) which always returns null.

Simplified:

<?php
$a = 123456;
var_dump($a[42]); // is null
$a = 123.45;
var_dump($a[42]); // is null
$a = true;
var_dump($a[42]); // is null
$a = null;
var_dump($a[42]); // is null

This "fails silently" as in theory you should get an error from this, rather than just null.

Also happens with null, other than int, float, bool:

<?php 
$a = true;
var_dump($a[42][42][42][42][42][42][42][42]); // also null, and no errors

But works correctly instead with arrays and strings.

<?php
$a = "abc";
var_dump($a[1]); // b
$a = [11, 22, 33];
var_dump($a[1]); // 22

Answering your question, "How does the “Array dereferencing” work on a scalar value of type": It doesn't, it just returns null instead of returning an error of some sort.