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PHP 7显著地改进了整体性能。确实有一些主要的特性，比如空合并操作符或返回类型声明。如果您不知道，可以通过查看文档去了解它们。

下面是一些可能有用的不太为人所知的特性。

命名空间

//before php7
use Universe\Saiyan;
use Universe\SuperSaiyan;
//in php7
use Universe\{Saiyan, SuperSaiyan};

常量数组

define('NAMES', [
'first'  => 'John',
'middle' => 'Fitzgerald',
'last'   => 'Kennedy'
]);
echo NAMES['last']; //displays "Kennedy"

太空船船操作符<=>

• 0： 相等
• 1： 左边的值大

• -1： 右边的值大

  $actressesWithAcademyAwards = [
  [ ‘name’ => ‘Katharine Hepburn’, ‘awards’ => 4 ],
  [ ‘name’ => ‘Jessica Lange’, ‘awards’ => 2 ],
  [ ‘name’ => ‘Meryl Streep’, ‘awards’ => 3 ],
  [ ‘name’ => ‘Cate Blanchett’, ‘awards’ => 2 ],
  ];
  usort($actressesWithAcademyAwards, function ($a, $b) {
  return $a[‘awards’] <=> $b[‘awards’];
  });

  print_r($actressesWithAcademyAwards);

数组第一/最后一键【php7.4】

$array = [ 'v' => 1, 'i' => 2, 'p' => 3 ];
$firstKey = array_key_first($array);
$lastKey = array_key_last($array);
print_r($firstKey); // v
print_r($lastKey); // p

扩展操作符【php7.4】

$abc = range('a', 'c');
$def = range('d', 'f');
$ghi = range('g', 'i');
$all = [...$abc, ...$def, ...$ghi, 'j'];
print_r($all);
//output
/*
Array
(
[0] => a
[1] => b
[2] => c
[3] => d
[4] => e
[5] => f
[6] => g
[7] => h
[8] => i
[9] => j
)*/

Arrow 函数【php7.4】

$c = 3;
$addC = fn($x) => $x + $c;
echo $addC(70); // 73

常量访问控制

class Mother {
private const ERROR_LEVEL_1 = 'achtung';
}