Object of class 'modelName' could not be converted to int in laravel - php

Question

I am trying to create an invoice number like - HCL/LF/02/2018 in where the number will be incremented by one for the new invoice. Would someone help me please to get expected invoice_no? I tried something like this in my controller -
public function create()
{
$check = OrderProformaInvoice::orderBy('created_at', 'DESC')->get();
$number = 01;
$year = date('Y');
if (count($check) > 0) {
$invoiceNo = OrderProformaInvoice::latest()->first(['invoice_no']);
$arr = array('HCL','LF', $invoiceNo + 1, $year);
$newInvoiceNo = implode("/",$arr);
}else{
$arr = array('HCL','LF', $number, $year);
$newInvoiceNo = implode("/",$arr);
}
return view('admin.marchendaising.order-proforma-invoices.create', compact('newInvoiceNo'));
}
And in my view form input field is-
<input type="text" name="invoice_no" class="form-control" value="{{ $newInvoiceNo }}">

Answer 1

You have mistake in this line:
$invoiceNo = OrderProformaInvoice::latest()->first(['invoice_no']);
Correct:
$invoiceNo = OrderProformaInvoice::latest()->get()->invoice_no;

Answer 2

You made a mistake here:
$invoiceNo = OrderProformaInvoice::latest()->first(['invoice_no']);
There was no need for this line since you already have a count of all of the OrderProformaInvoice so we may aswell set this to a variable and just increase it for a new one rather than making another call to the database.
If you ever were to delete a database record, you could use
$invoice = OrderProfromaInvoice::orderBy('created_at', 'desc')->first();
Then instead of $numOfInvoices++ you could do $invoice->id++ which will take the ID of the latest invoice and increment it by one.
public function create()
{
$check = OrderProformaInvoice::orderBy('created_at', 'DESC')->get();
$year = date('Y');
$numOfInvoices = count($check)
$arr = array('HCL','LF', $numOfInvoices++, $year);
$newInvoiceNo = implode("/",$arr);
// You could also just do this
$newInvoiceNo = 'HCL/LF/' . $numOfInvoices++ . '/' . $year;
// $newInvoiceNo will equal example: 'HCL/LF/12/2018';
return view('admin.marchendaising.order-proforma-invoices.create', compact('newInvoiceNo'));
}