A brief introduction to some of the eye-catching new features of PHP 7, a brief introduction to the new features_PHP Tutorial

A brief introduction to some eye-catching new features of PHP 7, a brief introduction to the new features

1. ?? operator (NULL coalescing operator)
I put this first because I find it useful. Usage:

$a = $_GET['a'] ?? 1;

It is equivalent to:

<&#63;php
$a = isset($_GET['a']) &#63; $_GET['a'] : 1;

We know that the ternary operator can be used like this:

$a ?: 1

But this is based on the premise that $a has been defined. The new ?? operator can simplify judgment.

2. Function return value type declaration
Example provided by the official documentation (note that the side length parameter syntax of ... is only available in PHP 5.6 and above):

<&#63;php
function arraysSum(array ...$arrays): array
{
  return array_map(function(array $array): int {
    return array_sum($array);
  }, $arrays);
}
print_r(arraysSum([1,2,3], [4,5,6], [7,8,9]));

It can be seen from this example that functions (including anonymous functions) can now specify the type of return value.

The way this statement is written is somewhat similar to swift:

func sayHello(personName: String) -> String {
  let greeting = "Hello, " + personName + "!"
  return greeting
}

This feature can help us avoid some problems caused by PHP's implicit type conversion. Thinking about the expected results before defining a function can avoid unnecessary mistakes.

However, there is also a feature that needs attention here. PHP 7 adds a declare directive: strict_types, which uses strict mode.

When using return value type declaration, if it is not declared in strict mode, and if the return value is not of the expected type, PHP will still cast it. But if it is strict mode, a Fatal error of TypeError will be triggered.

Forced mode:

<&#63;php
function foo($a) : int
{
  return $a;
}
foo(1.0);

The above code can be executed normally, and the foo function returns int 1 without any errors.

Strict mode:

<&#63;php
declare(strict_types=1);
function foo($a) : int
{
  return $a;
}
foo(1.0);
# PHP Fatal error: Uncaught TypeError: Return value of foo() must be of the type integer, float returned in test.php:6

After the declaration, a fatal error will be triggered.

Is it similar to the strict mode of js?

3. Scalar type declaration
The formal parameter type declaration of functions in PHP 7 can be scalar. In PHP 5, it can only be a class name, interface, array or callable (PHP 5.4, it can be a function, including anonymous functions). Now you can also use string, int, float and bool.

Official example:

<&#63;php
// Coercive mode
function sumOfInts(int ...$ints)
{
  return array_sum($ints);
}
var_dump(sumOfInts(2, '3', 4.1));

It should be noted that the strict mode problem mentioned above also applies here: in the forced mode (default, both forced type conversion), the parameters that do not meet the expectations will still be forced to type conversion, and in strict mode, it will be triggered TypeError fatal error.

4. use batch declaration
In PHP 7, use can declare multiple classes or functions or const in one sentence:

<&#63;php
use some\namespace\{ClassA, ClassB, ClassC as C};
use function some\namespace\{fn_a, fn_b, fn_c};
use const some\namespace\{ConstA, ConstB, ConstC};

But you still have to write the name of each class or function or const (there is no from some import * method like python).

A question to note is: If you are using a framework based on composer and PSR-4, can this writing method successfully load class files? In fact, it is possible. The autoloading method registered by composer searches the location according to the namespace of the class when the class is called. This way of writing has no effect on it.

5. Other features
I won’t introduce some other features one by one. If you are interested, you can check the official documentation: http://php.net/manual/en/migration70.new-features.php

Tell me a few briefly:

PHP 5.3 started to have anonymous functions, and now there are anonymous classes;
define can now define constant arrays;
Closure adds a call method;
Generators (or iterators, more appropriately) can have a final return value (return), or can be passed into another generator (generator delegate) through the new syntax of yield from.
Two new features of generators (return and yield from) can be combined. You can test the specific appearance by yourself. PHP 7 is now at RC5 and the final version should be coming soon.

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