spa-api/app/Models/LabelModal.php

<?php

namespace App\Models;

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

/**
 * 标签表
 */
class LabelModal extends Model
{
    //
    protected $table = 'labels';

    protected $guarded  = [];

    /**
     * 项目关联
     * @return BelongsToMany
     */
    public function projects(): BelongsToMany
    {
        return $this->belongsToMany(ProjectModal::class, 'project_labels_relations', 'label_id', 'project_id');
    }
}