Laravel Eloquent 多语言内容回退机制：优雅实现按优先级获取标题

CREATE TABLE `meta` (
    `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    `post_id` BIGINT UNSIGNED NOT NULL,
    `cat` VARCHAR(255) NOT NULL, -- 例如 'title', 'description'
    `meta_name` VARCHAR(255) NOT NULL, -- 例如 'en', 'nl', 'gr'
    `meta_value` TEXT NOT NULL,
    PRIMARY KEY (`id`),
    INDEX `meta_post_id_index` (`post_id`),
    FOREIGN KEY (`post_id`) REFERENCES `posts`(`id`) ON DELETE CASCADE
);

// app/Models/Post.php
namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;

class Post extends Model
{
    protected $fillable = ['slug']; // 假设有其他字段

    /**
     * 获取与文章相关的所有元数据。
     */
    public function metas(): HasMany
    {
        return $this->hasMany(Meta::class, 'post_id');
    }

    // 后续我们将在这里添加访问器
}

// app/Models/Meta.php
namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\BelongsTo;

class Meta extends Model
{
    protected $fillable = ['post_id', 'cat', 'meta_name', 'meta_value'];

    /**
     * 获取拥有此元数据的文章。
     */
    public function post(): BelongsTo
    {
        return $this->belongsTo(Post::class, 'post_id');
    }
}

use App\Models\Post;
use App\Models\Meta;

// 假设我们有一个文章ID
$postId = 1;

$post = Post::find($postId);
$title = null;

if ($post) {
    // 尝试获取英语标题
    $titleMeta = $post->metas()
                      ->where('cat', 'title')
                      ->where('meta_name', 'en')
                      ->first();

    if ($titleMeta) {
        $title = $titleMeta->meta_value;
    } else {
        // 如果英语标题不存在，尝试获取荷兰语标题
        $titleMeta = $post->metas()
                          ->where('cat', 'title')
                          ->where('meta_name', 'nl')
                          ->first();
        if ($titleMeta) {
            $title = $titleMeta->meta_value;
        } else {
            // 如果荷兰语标题也不存在，尝试获取希腊语标题
            $titleMeta = $post->metas()
                              ->where('cat', 'title')
                              ->where('meta_name', 'gr')
                              ->first();
            if ($titleMeta) {
                $title = $titleMeta->meta_value;
            }
        }
    }
}

echo $title ?? '标题未找到';

use App\Models\Post;
use App\Models\Meta;

// 假设我们有一个文章ID
$postId =