Deposit.php

<?php

class Deposit extends OperationBaseModel {
    protected $guarded = array();
    
    public static $rules = array(
        'deposit_amount'  => 'required',
        'approval_status' => 'required'
    );
}

DepositObserver.php

<?php

class DepositObserver {
    public function creating($model) {
        // I would prefer to change from static to public method.
        $deposit->reference_no = $this->generateReferenceNo(Config::get('referenceNo.depositPrefix'));
        
        DB::table('deposit_status')->where('name', '=', 'Pending')->increment('record_count');
    }
}

start.php

Deposit::observe(new UserReferenceObserver(Sentry::user()));
Deposit::observe(new DepositObserver);

UserReferenceObserver.php

<?php

class UserReferenceObserver {
    protected $user;
    
    public function __construct($user) {
        $this->user = $user;
    }
    
    public function saving($model) {
        $model->updated_by = $this->user->id;
    }
}