箭头函数 #

<?php
$add = fn(int $a, int $b) => $a + $b;

echo $add(1, 2);

<?php
$add = function(int $a, int $b): int {
    return $a + $b;
};

$add = fn(int $a, int $b) => $a + $b;

<?php
$square = fn($n) => $n ** 2;
$greet = fn($name) => "Hello, $name!";
$isEven = fn($n) => $n % 2 === 0;

<?php
fn(参数列表) => 表达式

<?php
$getTime = fn() => time();
$pi = fn() => M_PI;

echo $getTime();
echo $pi();

<?php
$double = fn($n) => $n * 2;
$upper = fn($s) => strtoupper($s);

echo $double(5);
echo $upper("hello");

<?php
$add = fn($a, $b) => $a + $b;
$format = fn($name, $age) => "$name is $age years old";

echo $add(1, 2);
echo $format("John", 25);

<?php
$add = fn(int $a, int $b): int => $a + $b;
$greet = fn(string $name): string => "Hello, $name!";

echo $add(1, 2);
echo $greet("John");

<?php
$sum = fn(...$numbers) => array_sum($numbers);

echo $sum(1, 2, 3, 4, 5);

<?php
$message = "Hello";

$greet = fn($name) => "$message, $name!";

echo $greet("John");

<?php
$factor = 10;

$multiply = function($n) use ($factor) {
    return $n * $factor;
};

$multiply = fn($n) => $n * $factor;

<?php
$counter = 0;

$increment = fn() => ++$counter;

echo $increment();
echo $counter;

<?php
$prefix = "Hello";
$suffix = "!";

$greet = fn($name) => "$prefix, $name$suffix";

echo $greet("John");

<?php
$numbers = [1, 2, 3, 4, 5];

$squared = array_map(fn($n) => $n ** 2, $numbers);
$doubled = array_map(fn($n) => $n * 2, $numbers);

print_r($squared);
print_r($doubled);

<?php
$numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

$even = array_filter($numbers, fn($n) => $n % 2 === 0);
$greaterThan5 = array_filter($numbers, fn($n) => $n > 5);

print_r($even);
print_r($greaterThan5);

<?php
$numbers = [1, 2, 3, 4, 5];

$sum = array_reduce($numbers, fn($carry, $n) => $carry + $n, 0);
$product = array_reduce($numbers, fn($carry, $n) => $carry * $n, 1);

echo $sum;
echo $product;

<?php
$users = [
    ['name' => 'John', 'age' => 25],
    ['name' => 'Jane', 'age' => 30],
    ['name' => 'Bob', 'age' => 20]
];

usort($users, fn($a, $b) => $a['age'] <=> $b['age']);

print_r($users);

<?php
$users = [
    ['id' => 1, 'name' => 'John'],
    ['id' => 2, 'name' => 'Jane']
];

$names = array_map(fn($u) => $u['name'], $users);
$ids = array_map(fn($u) => $u['id'], $users);

print_r($names);
print_r($ids);

<?php
class User
{
    public function __construct(
        public string $name,
        public int $age
    ) {}
}

$user = new User("John", 25);

$getName = fn() => $user->name;
$getAge = fn() => $user->age;

echo $getName();
echo $getAge();

<?php
class Calculator
{
    public function add(int $a, int $b): int
    {
        return $a + $b;
    }
}

$calc = new Calculator();
$add = fn($a, $b) => $calc->add($a, $b);

echo $add(1, 2);

<?php
function createMultiplier(int $factor): callable
{
    return fn($n) => $n * $factor;
}

$double = createMultiplier(2);
$triple = createMultiplier(3);

echo $double(5);
echo $triple(5);

<?php
$compose = fn($f, $g) => fn($x) => $f($g($x));

$addOne = fn($x) => $x + 1;
$double = fn($x) => $x * 2;

$addOneThenDouble = $compose($double, $addOne);
echo $addOneThenDouble(5);

<?php
$valid = fn($n) => $n > 0 && $n < 100;

$invalid = fn($n) => {
    $result = $n * 2;
    return $result;
};

$valid = fn($n) => $n * 2;

<?php
$counter = 0;

$increment = fn() => ++$counter;

$increment = function() use (&$counter) {
    return ++$counter;
};

<?php
$invalid = fn() => static $count = 0;

<?php
$products = [
    ['name' => 'Apple', 'price' => 100],
    ['name' => 'Banana', 'price' => 50],
    ['name' => 'Cherry', 'price' => 200]
];

$taxRate = 0.1;

$withTax = array_map(
    fn($p) => [...$p, 'priceWithTax' => $p['price'] * (1 + $taxRate)],
    $products
);

print_r($withTax);

<?php
$users = [
    ['name' => 'John', 'active' => true, 'role' => 'admin'],
    ['name' => 'Jane', 'active' => false, 'role' => 'user'],
    ['name' => 'Bob', 'active' => true, 'role' => 'user']
];

$activeAdmins = array_filter(
    $users,
    fn($u) => $u['active'] && $u['role'] === 'admin'
);

print_r($activeAdmins);

<?php
$items = [
    ['name' => 'C', 'order' => 3],
    ['name' => 'A', 'order' => 1],
    ['name' => 'B', 'order' => 2]
];

usort($items, fn($a, $b) => $a['order'] <=> $b['order']);

print_r($items);

<?php
$strings = ['hello', 'world', 'php'];

$upper = array_map(fn($s) => strtoupper($s), $strings);
$lengths = array_map(fn($s) => strlen($s), $strings);

print_r($upper);
print_r($lengths);

<?php
$squared = array_map(fn($n) => $n ** 2, $numbers);
$even = array_filter($numbers, fn($n) => $n % 2 === 0);

<?php
$processed = array_map(function($item) {
    $result = complexCalculation($item);
    logResult($result);
    return $result;
}, $items);

<?php
$counter = 0;

$increment = function() use (&$counter) {
    return ++$counter;
};