list pending po pending approval

app/Invoice.php

@@ -9,7 +9,7 @@ class Invoice extends Model
     protected $fillable = ['invoice_url','amount','booking_id', 'buyer_company', 'address', 'contact_no', 'po_number', 'adjustment'];
 
     public function booking(){
-        return $this->belongsTo('App\Booking');
+        return $this->belongsTo(Booking::class);
     }
 
     public function invoiceDetails() {

app/InvoiceDetails.php

@@ -9,6 +9,6 @@ class InvoiceDetails extends Model
     protected $fillable = ['invoice_id', 'order','description','quantity', 'stock_code', 'unit_price_rmb', 'unit_price_rm', 'total'];
     
     public function invoice() {
-        return $this->belongsTo('App/Invoice');
+        return $this->belongsTo(Invoice::class);
     }
 }