PHP 8.2 : Disjunctive Normal Form (DNF) Types

PHP 8.2 introduces a new feature called Disjunctive Normal Form (DNF) Types, which allow developers to specify complex type constraints using logical OR and AND operators. This can be useful in cases where a variable may need to satisfy multiple type constraints at once.

To use DNF Types, developers can use the | operator to specify that a variable must satisfy at least one of multiple type constraints, and the & operator to specify that a variable must satisfy all of multiple type constraints.

For example, consider the following code:

function process_data(int | string | array $data) {
// code to process data
}process_data(123); // valid
process_data(“hello”); // valid
process_data([“a”, “b”, “c”]); // valid
process_data(true); // invalid

In this case, the process_data function is expecting a variable that is either an integer, a string, or an array. This allows the function to handle different types of data without requiring multiple versions of the function for each type.

We can also use the & operator to specify that a variable must satisfy multiple type constraints at once. For example:

function process_data(array & string $data) {
// code to process data
}process_data(123); // invalid
process_data(“hello”); // valid

In this case, the process_data function is expecting a variable that is both an integer and a string. This would be a rare case, but it illustrates how the & operator can be used to specify complex type constraints.

It’s important to note that DNF Types are not the same as union types. Union types allow you to specify multiple possible types for a single variable, while DNF Types allow you to specify complex type constraints using logical operators.

Overall, DNF Types provide a convenient way for developers to specify complex type constraints using logical OR and AND operators, making it easier to ensure that data is being passed correctly throughout the code.