type.php

<?php

namespace SUN\Models\ESI;

use Illuminate\Database\Eloquent\Model;

class Type extends Model
{
...
    public function skillz()
    {
        return $this->belongsToMany(Type::class, 'type_skillz', 'type_id', 'skill_id');
    }
    
    public function p_types ()
    {
        return $this->belongsToMany(Type::class, 'type_skillz', 'skill_id', 'type_id');
    }
}