Let's take a look at the new features of each version of PHP 7.x

New features of PHP 7.x in each version

Preface

Last month my colleague saw me writing

$a = $a ?? '';

and asked me what this way of writing is, is there any other way of writing it? I said this is a writing method that is only available in PHP7 and above. Don’t you know? He said he didn't know.

I muttered in my heart and planned to start writing this blog.

PHP7 should be a modern PHP in addition to the basics. Because in PHP7, strong type definitions and some grammatical writing methods, such as combined comparison operators, define() can define arrays and other features. The formal introduction begins below, starting with PHP7.0. New versions will be added in the future, and they will be added one after another.
Ok, let’s start

PHP 7.0

Scalar type declaration

What is a scalar type?

Four scalar types:
boolean (Boolean type)
integer (integer type)
float (floating point type, also called double)
string (character String)
Two composite types:
array (array)
object (object)
Resource is a special variable that holds a reference to an external resource. Resources are created and used through specialized functions. Resource type variables are special handles for opening files, database connections, graphics canvas areas, etc.
To put it more simply, a scalar type is a data type that defines variables.

In php5, there are class names, interfaces, arrays and callback functions. In PHP, strings, integers, floats, and bools have been added. Let's take an example below. See the example for everything

function typeInt(int $a){
    echo $a;}typeInt('sad');// 运行，他讲会报错 Fatal error: Uncaught TypeError: Argument 1 passed to type() must be of the type integer, string given

Here, we define that $a must be of type int. If string is passed in the type function, an error will be reported. Let's modify the above code.

function typeString(string $a){
    echo $a;}typeString('sad'); //sad

Return value type declaration

The method return value of the function can be defined. For example, a certain function of mine must return Int type, it will definitely return int. If you return string, an error will be reported. As follows

<?phpfunction returnArray(): array{

    return [1, 2, 3, 4];}print_r(returnArray());/*Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
)
*/

What happens when we define an array and return string or other types?

Then he willreport an errorFor example

function returnErrorArray(): array
{

    return '1456546';
}

print_r(returnErrorArray());
/*
Array
Fatal error: Uncaught TypeError: Return value of returnArray() must be of the type array, string returned in 
*/

null merge operator

Due to the fact that there are a large number of three simultaneous uses in daily use In the case of metaexpressions and isset(), we add the syntactic sugar of the null coalescing operator (??). If the variable exists and is not NULL, it returns its own value, otherwise it returns its second operand.

<?php

$username = $_GET[&#39;user&#39;] ?? &#39;nobody&#39;;
//这两个是等效的  当不存在user 则返回?? 后面的参数

$username = isset($_GET[&#39;user&#39;]) ? $_GET[&#39;user&#39;] : &#39;nobody&#39;;

?>

Spaceship operator

// 整数echo 1 <=> 1; // 0 当左边等于右边的时候，返回0echo 1 <=> 2; // -1  当左边小于右边，返回-1echo 2 <=> 1; // 1  当左边大于右边，返回1// 浮点数echo 1.5 <=> 1.5; // 0echo 1.5 <=> 2.5; // -1echo 2.5 <=> 1.5; // 1
 // 字符串echo "a" <=> "a"; // 0echo "a" <=> "b"; // -1echo "b" <=> "a"; // 1

define Define array

In versions prior to PHP7, define cannot define arrays It is now possible, for example,

define('ANIMALS', [
    'dog',
    'cat',
    'bird'
]);

echo ANIMALS[1]; // 输出 "cat"

use method batch import

// PHP 7 之前的代码use some\namespace\ClassA;use some\namespace\ClassB;use some\namespace\ClassC as C;use function some\namespace\fn_a;use function some\namespace\fn_b;use function some\namespace\fn_c;use const some\namespace\ConstA;use const some\namespace\ConstB;use const some\namespace\ConstC;// PHP 7+ 及更高版本的代码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};

echo "\u{aa}"; //ªecho "\u{0000aa}";  //ª  echo "\u{9999}"; //香

<?phpinterface Logger {
    public function log(string $msg);}class Application {
    private $logger;

    public function getLogger(): Logger {
         return $this->logger;
    }

    public function setLogger(Logger $logger) {
         $this->logger = $logger;
    }}$app = new Application;$app->setLogger(new class implements Logger {  //这里就是匿名类
    public function log(string $msg) {
        echo $msg;
    }});

Nullable types

<?phpfunction testReturn(): ?string{
    return &#39;elePHPant&#39;;}var_dump(testReturn()); //string(10) "elePHPant"function testReturn(): ?string{
    return null;}var_dump(testReturn()); //NULLfunction test(?string $name){
    var_dump($name);}test(&#39;elePHPant&#39;); //string(10) "elePHPant"test(null); //NULLtest(); //Uncaught Error: Too few arguments to function test(), 0 passed in...

<?phpfunction swap(&$left, &$right) : void{
    if ($left === $right) {
        return;
    }

    $tmp = $left;
    $left = $right;
    $right = $tmp;}$a = 1;$b = 2;var_dump(swap($a, $b), $a, $b);

<?php
try {
    // some code
} catch (FirstException | SecondException $e) {  //用 | 来捕获FirstException异常，或者SecondException 异常
  
}

For example,

<?phpuse Foo\Bar\{
    Foo,
    Bar,
    Baz,};

<?phpabstract class A{
    abstract function test(string $s);}abstract class B extends A{
    // overridden - still maintaining contravariance for parameters and covariance for return
    abstract function test($s) : int;}

<?phpfunction test(object $obj) : object  //这里 可以输入对象{
    return new SplQueue();}test(new StdClass());

PHP7.3 There are no big changes at the syntax level.

Congratulations on PHP taking another step towards strong typing

<?phpclass User {
    public int $id;
    public string $name;}?>

<?php$factor = 10;$nums = array_map(fn($n) => $n * $factor, [1, 2, 3, 4]);// $nums = array(10, 20, 30, 40);?>

<?php$array[&#39;key&#39;] ??= computeDefault();// 类似与这个if (!isset($array[&#39;key&#39;])) {
    $array[&#39;key&#39;] = computeDefault();}?>