Nullable¶
Nullable is the name of the NULL value, when used as a type. Until PHP 8.0, it was marked as a question mark with types, and since PHP 8.0, it is also marked with its own name, as an union type.
<?php
function foo(?A $a) : null | B {
// code
}
?>
See also Dealing with null
Related : Null, Type System, Contravariance
Added in PHP 7.1
