function setAge(int $age) {
  var_dump($age);
}
// 要求传入参数是整型
// echo setAge('dwdw');
// Fatal error: Uncaught TypeError: Argument 1 passed to setAge() must be of the type integer, string given...
// 注意这么写不会报错
echo setAge('1');

class User {}

function getUser() : array {
  return new User;
}
// Fatal error: Uncaught TypeError: Return value of getUser() must be of the type array, object returned
var_dump(getUser());
// 改成下面不会报错
function getUser() : User {
  return new User;
}

// 如果返回的类型不对
function getUser() : User {
	return [];
}
// 会报
// Fatal error: Uncaught TypeError: Return value of getUser() must be an instance of User, array returned 


// 再来个interface的例子, 执行下面的不会报错
interface SomeInterFace {
	public function getUser() : User;
}

class User {}

class SomeClass implements SomeInterFace {
	public function getUser() : User {
		return [];
	}
}
// 但是当调用的时候才会检查返回类型
// Fatal error: Uncaught TypeError: Return value of SomeClass::getUser() must be an instance of User, array returned
(new SomeClass)->getUser();

// Integers
echo 1 <=> 1; // 0
echo 1 <=> 2; // -1
echo 2 <=> 1; // 1

// 在usort自定义排序方法中很好用

$arr = ['c', 'd', 'b', 'a'];
// ['a', 'b', 'c', 'd']
usort($arr, function($a, $b) {
  return $a <=> $b;
});

use App\Model\User;
use App\Model\Cart;
use App\Model\Base\BaseUser;

use App\Model\{
  User,
  Cart,
  Base\BaseUser
};

php

class SomeClass {}
interface SomeInterface {}
trait SomeTrait {}

var_dump(new class(10) extends SomeClass implements SomeInterface {
    private $num;

    public function __construct($num)
    {
        $this->num = $num;
    }

    use SomeTrait;
});
// 输出
object(class@anonymous)[1]
  private 'num' => int 10

php

<?php
$b = array();
each($b);

// Deprecated:  The each() function is deprecated. This message will be suppressed on further calls

php

function fun_adm_each(&$array){
   $res = array();
   $key = key($array);
   if($key !== null){
       next($array); 
       $res[1] = $res['value'] = $array[$key];
       $res[0] = $res['key'] = $key;
   }else{
       $res = false;
   }
   return $res;
}

<?php

count('');

// Warning:  count(): Parameter must be an array or an object that implements Countable

php

function fun_adm_count($array_or_countable,$mode = COUNT_NORMAL){
    if(is_array($array_or_countable) || is_object($array_or_countable)){
        return count($array_or_countable, $mode);
    }else{
        return 0;
    }
}