Understanding PHP’s Null Coalescing Operator (??)

The Null Coalescing Operator (??)

Introduced in PHP 7.0, the null coalescing operator, represented by ??, is a simple but effective feature for streamlining code. It allows for cleaner, more readable handling of null or unset variables.

The primary use of ?? is to check if a variable is set and not null. If it's either unset or null, the operator allows you to provide a default value.

For example:

$name = $_GET['name'] ?? 'Unknown';

In this code, $name is assigned the value of $_GET['name'] if it is set and not null. If not, it defaults to "Unknown".

The operator can also be chained to check multiple variables:

$foo = $foo ?? $bar ?? 'baz';

Here, PHP first checks $foo. If it's null or unset, it checks $bar. If neither is set, it assigns the value 'baz'.

The Null Coalescing Assignment Operator (??=)

PHP 7.4 introduced the null coalescing assignment operator (??=), which simplifies the process of assigning a value to a variable only if that variable is not already set or is null.

For example, in a function where a parameter may or may not be passed: