LMS/app/Models/CourseCategory.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;
use Illuminate\Database\Eloquent\Relations\BelongsTo;

class CourseCategory extends Model
{
    use HasFactory;

    protected $fillable = [
        'parent_id',
        'name',
        'slug',
        'description',
        'sort_order',
        'is_active',
    ];

    protected $casts = [
        'is_active' => 'boolean',
    ];

    public function parent(): BelongsTo
    {
        return $this->belongsTo(CourseCategory::class, 'parent_id');
    }

    public function children(): HasMany
    {
        return $this->hasMany(CourseCategory::class, 'parent_id');
    }

    public function courses(): HasMany
    {
        return $this->hasMany(Course::class);
    }

    public function scopeTree($query)
    {
        return $query->with(['children', 'children.children'])->withCount('courses')->orderBy('sort_order')->get()->filter(function($cat) {
            return is_null($cat->parent_id);
        });
    }
}