Prague2024-06-20

Data types and type declarations in PHP 8

As a programming language, PHP has been around for over 25 years and has undergone several changes and improvements. One of the major changes in the latest version of PHP, PHP 8, is the introduction of new data types and improvements in type declarations. In this article, we will explore the new data types and type declarations in PHP 8.

Data Types in PHP 8 PHP 8 introduces two new data types, which are the union types and the just-in-time (JIT) compiled types.

Union Types

Union types allow you to declare a parameter, property, or return value that can have more than one data type. This is useful when you need to specify a range of possible data types that a value can take. For example, you could use a union type to define a parameter that can accept both integers and floats. The syntax for defining a union type is to separate each data type with a pipe character (|).

JIT Compiled Types

Just-in-time (JIT) compilation is a technique used to improve the performance of PHP scripts. In PHP 8, JIT compilation is used to improve the performance of certain data types. Specifically, JIT compilation is used to speed up the processing of strings, arrays, and function calls.

Type Declarations in PHP 8

Type declarations are used to specify the data type of a variable, parameter, or return value. PHP 8 introduces several improvements to type declarations, including stricter type checking and more precise type hinting.

Stricter Type Checking

In previous versions of PHP, type declarations were optional, and PHP would automatically convert values to the expected data type. In PHP 8, type declarations are stricter, and PHP will throw a TypeError if a value does not match the expected data type. This helps to catch errors earlier in the development process and improve the overall reliability of PHP code.

Precise Type Hinting

PHP 8 introduces two new type hints, which are the mixed type and the static type. The mixed type allows you to specify that a parameter or return value can have any data type, while the static type allows you to specify that a parameter or return value should have the same data type as the object that the method is called on.

In conclusion, PHP 8 introduces several new data types and improvements to type declarations. These changes make it easier to write reliable, high-performance PHP code. By using union types, JIT compiled types, and stricter type checking, developers can write more robust code that is less prone to errors. The introduction of mixed and static type hints also allows for more precise type hinting, which can make code easier to read and understand. Overall, PHP 8 is a significant improvement over previous versions of PHP and is well worth upgrading to for any PHP developer.

Code examples

Here are some code examples to help illustrate the concepts discussed in the article:

Union Types:

function exampleFunction(int|float $number): void {
  // Function body
}

In this example, we’re defining a function called exampleFunction that takes a parameter called $number. We’re using a union type to specify that $number can be either an integer or a float. This means that if we call exampleFunction with an integer or a float value, PHP will not throw an error.

JIT Compiled Types:

$array = [1, 2, 3];
$result = array_map(fn($n) => $n * 2, $array);

In this example, we’re using the array_map function to apply a callback function to each element in an array. In PHP 8, the array_map function is JIT compiled, which means that it will execute faster than it would in previous versions of PHP.

Stricter Type Checking:

function divide(int $a, int $b): float {
  return $a / $b;
}

// This will work
$result = divide(4, 2); // Returns 2.0 (a float)

// This will throw a TypeError
$result = divide(4, '2'); // Throws a TypeError because the second parameter is a string, not an integer

In this example, we’re defining a function called divide that takes two parameters, $a and $b, both of which are expected to be integers. The function then returns the result of dividing $a by $b, but since the result could be a float, we specify that the function should return a float.

In the first function call, we pass in the integers 4 and 2 as the arguments, and the function correctly returns a float value of 2.0.

In the second function call, however, we pass in the integer 4 and the string ‘2’ as the arguments. Since the second argument is not an integer, PHP 8 will throw a TypeError, indicating that the argument is of the wrong data type.

This demonstrates how stricter type checking in PHP 8 can help catch errors earlier in the development process and improve the overall reliability of PHP code.

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