PHP: Types, Arrays, Classes, Namespaces and Composer Reference Guide

# Install
brew install php@8.3                   # macOS
sudo apt install php8.3-cli php8.3-mbstring php8.3-curl php8.3-xml
# Windows: https://windows.php.net/download/

# Composer (the dep manager)
curl -sS https://getcomposer.org/installer | php
sudo mv composer.phar /usr/local/bin/composer

# New project
mkdir myapp && cd myapp
composer init                          # interactive — fills composer.json
composer require slim/slim guzzlehttp/guzzle
composer require --dev phpunit/phpunit phpstan/phpstan

# Run
php -S 127.0.0.1:8000 -t public        # built-in dev server
php script.php                         # run a CLI script

# Daily commands
composer dump-autoload                 # regenerate autoloader
vendor/bin/phpunit
vendor/bin/phpstan analyse --level=max src
vendor/bin/php-cs-fixer fix

 36, 'grace' => 85];

// Spread + destructuring
$more = [...$nums, 5, 6];
[$a, $b, $rest] = [1, 2, [3, 4]];
['ada' => $age] = $users;              // named destructure

// Common helpers
$doubled = array_map(fn($x) => $x * 2, $nums);
$evens   = array_filter($nums, fn($x) => $x % 2 === 0);
$sum     = array_reduce($nums, fn($acc, $x) => $acc + $x, 0);

// Indexed vs associative
$names = array_keys($users);
$ages  = array_values($users);
$has   = array_key_exists('ada', $users);
sort($nums);                            // mutates! in-place

// Grouping
$grouped = [];
foreach ($users as $name => $age) {
    $bucket = $age >= 50 ? 'senior' : 'junior';
    $grouped[$bucket][] = $name;
}
print_r($grouped);

// First-class callable syntax (PHP 8.1+)
$upper = strtoupper(...);
echo $upper('hello');                   // "HELLO"

id, $this->name, $email);
    }
}

// Backed enum — values map to int/string
enum Role: string
{
    case Admin  = 'admin';
    case Member = 'member';
    case Guest  = 'guest';

    public function isPrivileged(): bool
    {
        return match ($this) {
            self::Admin           => true,
            self::Member, self::Guest => false,
        };
    }
}

// Interface + readonly + match expression
interface Repository
{
    public function find(string $id): ?User;
}

class InMemoryUsers implements Repository
{
    /** @var array */
    private array $store = [];

    public function upsert(User $u): void { $this->store[$u->id] = $u; }
    public function find(string $id): ?User { return $this->store[$id] ?? null; }
}

 'https://api.github.com/',
    'headers'  => ['User-Agent' => 'devshelf'],
    'timeout'  => 5.0,
]);

$owners = ['php', 'symfony', 'laravel'];

// Concurrent fan-out via Guzzle promises
$promises = [];
foreach ($owners as $owner) {
    $promises[$owner] = $client->getAsync("users/{$owner}/repos?per_page=5");
}

// Wait for all; settled = no exceptions on individual failures
$results = Utils::settle($promises)->wait();

foreach ($results as $owner => $r) {
    if ($r['state'] !== 'fulfilled') {
        fwrite(STDERR, "{$owner}: " . $r['reason']->getMessage() . "\n");
        continue;
    }
    $repos = json_decode((string) $r['value']->getBody(), true, flags: JSON_THROW_ON_ERROR);
    foreach ($repos as $repo) {
        printf("%s/%s ★%d\n", $owner, $repo['name'], $repo['stargazers_count']);
    }
}