Neutral Element

A neutral element is an piece of data which has no effect with a particular operation.

For example, 0 is the neutral element for the addition, as 0 + $a is the same as $a + 0 and the same as $a (without any type change).

The neutral element for the multiplication is 1; the neutral element for the concatenation is the empty string ''.

It is usually possible to define a neutral element for any operation or method call. For objects, they are call null object, as they could replace the null scalar value.

<?php

$a = 10;

$a *= 1; // this does nothing
$a += 1; // this does nothing

?>

Documentation

See also Null Object Pattern