<?php


//IT SHOULD BE INSIDE YOUR MEHTOD

//get last record
$record = RecordModel::latest()->first();
$expNum = explode('-', $record->invoiceno);


//check first day in a year
if ( date('l',strtotime(date('Y-01-01'))) ){
    $nextInvoiceNumber = date('Y').'-0001';
} else {
    //increase 1 with last invoice number
    $nextInvoiceNumber = $expNum[0].'-'. $expNum[1]+1;
}


//Now add New record into database