surveyor_indonesia_backend/app/Models/AssignMaterial.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use App\Models\RequestMaterial;
use App\Models\Activity;
use Carbon\Carbon;

class AssignMaterial extends Model
{
    protected $table = 'assign_material_to_activity';

    const CREATED_AT = 'created_at';
    const UPDATED_AT = 'updated_at';

    protected $fillable = [
        'proyek_id', 'activity_id', 'material_id', 'qty_planning', 'budget', 'plan_date','created_at', 'created_by', 'updated_at', 'updated_by'
	];

	protected $casts = [
        'id' => 'integer',
        'budget' => 'string',
    ];

	public static function boot() {
		parent::boot();

		static::created(function($data) {
			$activity = Activity::find($data->activity_id);
			$material = RequestMaterial::where("id", $data->material_id)->first();
			$activity->rencana_biaya += floatval($material->price) * floatval($data->qty_planning);
			$activity->save();
		});

		static::deleted(function($data) {
			$activity = Activity::where('id', $data->activity_id)->first();
			$activity->rencana_biaya -= floatval($data->budget) * floatval($data->qty_planning);
			$activity->save();
		});

	}
}