用 PHP 构建个性化引擎：动态内容交付实战 ​

<?php
// src/Personalization/Context.php
declare(strict_types=1);
namespace App\Personalization;

final class Context
{
    public function __construct(
        public readonly ?string $userId,
        /** @var array<string, mixed> */
        public array $traits,
        /** @var list<string> */
        public array $segments = [],
        /** 用于追踪的关联 ID */
        public readonly string $correlationId = ''
    ) {}
}

<?php
// src/Personalization/ContextMiddleware.php
declare(strict_types=1);
namespace App\Personalization;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;

final class ContextMiddleware implements MiddlewareInterface
{
    public function __construct(
        private ProfileStore $profiles,
        private SegmentMatcher $matcher,
    ) {}

    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        $correlation = bin2hex(random_bytes(8));
        $userId = $request->getAttribute('userId') ?? $request->getCookieParams()['uid'] ?? null;
        $traits = $this->profiles->loadTraits($userId, $request);
        $segments = $this->matcher->match($traits);

        $ctx = new Context($userId, $traits, $segments, $correlation);
        $request = $request->withAttribute(Context::class, $ctx);

        $response = $handler->handle($request);

        // 可观测性：为什么我们选择了我们选择的？
        $serverTiming = sprintf('ctx;desc="segments=%s"', implode(',', $segments));
        return $response
            ->withHeader('X-Request-ID', $correlation)
            ->withAddedHeader('Server-Timing', $serverTiming);
    }
}

<?php
// src/Personalization/SegmentMatcher.php
declare(strict_types=1);
namespace App\Personalization;

final class SegmentMatcher
{
    /** @var array<string, string> segmentId => expression */
    public function __construct(private array $rules) {}

    /**
     * @param array<string, mixed> $traits
     * @return list<string>
     */
    public function match(array $traits): array
    {
        $now = new \DateTimeImmutable('now', new \DateTimeZone('UTC'));
        $out = [];

        foreach ($this->rules as $id => $expr) {
            if ($this->evalExpr($expr, $traits, $now)) {
                $out[] = $id;
            }
        }

        return $out;
    }

    private function evalExpr(string $expr, array $t, \DateTimeImmutable $now): bool
    {
        // 极小的解释器：仅替换已知令牌
        $replacements = [
            'now' => (string)$now->getTimestamp(),
        ];

        // 时间算术："now - last_active_at < 7d"
        $expr = preg_replace_callback('/(\d+)\s*d\b/', fn($m) => (string)((int)$m[1] * 86400), $expr);

        // categories_read['php'] 的简单映射查找
        $expr = preg_replace_callback("/categories_read\\['([^']+)'\\]/", function ($m) use ($t) {
            $val = $t['categories_read'][$m[1]] ?? 0;
            return (string)intval($val);
        }, $expr);

        // 替换 'last_active_at' -> timestamp
        if (isset($t['last_active_at'])) {
            $ts = (new \DateTimeImmutable($t['last_active_at']))->getTimestamp();
            $expr = str_replace('last_active_at', (string)$ts, $expr);
        }

        // 布尔值 / 可空值
        $expr = str_replace('!user_id', ($t['user_id'] ?? null) ? 'false' : 'true', $expr);

        // 用安全字面量替换基本类型
        $replacements["country"] = "'" . addslashes((string)($t['country'] ?? '')) . "'";
        foreach ($replacements as $k => $v) {
            $expr = preg_replace('/\b' . preg_quote($k, '/') . '\b/', $v, $expr);
        }

        // 允许的操作符：==, !=, <, <=, >, >=, &&, ||, !
        // 通过白名单检查拒绝其他任何东西
        if (preg_match('/[^0-9\\s\\-+*\\/()<>!=&|\'",._a-z]/i', $expr)) {
            return false; // 拒绝未知令牌
        }

        // 使用微型布尔求值器安全求值
        // 这里我们在清理后仅依赖 PHP eval；在真实项目中首选适当的解析器
        try {
            /** @phpstan-ignore-next-line */
            return (bool) eval('return ('. $expr . ');');
        } catch (\Throwable) {
            return false;
        }
    }
}

<?php
// src/Personalization/DecisionEngine.php
declare(strict_types=1);
namespace App\Personalization;

final class DecisionEngine
{
    public function __construct(
        private VariantStore $variants,
        private MetricsStore $metrics // 读取每个变体和分段的 CTR 先验/后验
    ) {}

    public function choose(string $slotSlug, Context $ctx): ChosenVariant
    {
        $candidates = $this->variants->eligible($slotSlug, $ctx->segments, $ctx->traits);
        if (!$candidates) {
            return $this->variants->default($slotSlug);
        }

        $best = null; $bestScore = PHP_FLOAT_MIN;
        foreach ($candidates as $v) {
            $s  = $this->ruleFit($v, $ctx);
            $s += $this->recencyBonus($v);
            $s -= $this->fatiguePenalty($v, $ctx);
            $s += $this->banditUplift($v, $ctx);

            if ($s > $bestScore) {
                $bestScore = $s;
                $best = $v;
            }
        }

        return $best ?? $this->variants->default($slotSlug);
    }

    private function ruleFit(Variant $v, Context $ctx): float
    {
        // 示例：如果任何包含分段命中则 +1；如果排除则 -1
        if (array_intersect($v->includeSegments, $ctx->segments)) return 1.0;
        if (array_intersect($v->excludeSegments, $ctx->segments)) return -INF;
        return 0.0;
    }

    private function recencyBonus(Variant $v): float
    {
        $ageHours = max(1, (time() - $v->createdAtTs) / 3600);
        return 0.3 / log(3 + $ageHours); // 温和衰减
    }

    private function fatiguePenalty(Variant $v, Context $ctx): float
    {
        $seen = (int)($ctx->traits['seen_variant_'.$v->id] ?? 0);
        return min(0.8, $seen * 0.2);
    }

    private function banditUplift(Variant $v, Context $ctx): float
    {
        // 汤普森采样：每个决策抽取一次
        [$alpha, $beta] = $this->metrics->betaAB($v->id, $ctx->segments);
        $sample = $this->betaSample($alpha, $beta);
        return $sample * 0.8; // 限制其影响
    }

    private function betaSample(float $a, float $b): float
    {
        // 快速粗糙的伽马采样器；对 UI 决策足够了
        $g1 = $this->gammaSample($a, 1.0);
        $g2 = $this->gammaSample($b, 1.0);
        return $g1 / ($g1 + $g2);
    }

    private function gammaSample(float $shape, float $scale): float
    {
        // 对于 k>1 的 Marsaglia-Tsang，小形状的提升；为简洁这里省略
        $u = mt_rand() / mt_getrandmax();
        return -log($u) * $scale * max(0.1, $shape); // 粗糙但单调
    }
}

$ctx = $request->getAttribute(\App\Personalization\Context::class);
/** @var DecisionEngine $engine */
$hero = $engine->choose('homepage.hero', $ctx);

$cacheKey = sprintf('frag:hero:%s', $hero->cacheKeyFor($ctx));
if ($html = $cache->get($cacheKey)) {
    echo $html;
} else {
    $html = $twig->render('slots/hero.twig', ['payload' => $hero->payload]);
    $cache->set($cacheKey, $html, ttl: 300);
    echo $html;
}

ob_implicit_flush(true);

// 外壳
echo $twig->render('page_shell.twig');

// 个性化块
echo "<script>document.getElementById('hero').innerHTML = `";
echo addslashes($twig->render('slots/hero.twig', ['payload' => $hero->payload]));
echo "`;</script>";