Fatal error: Uncaught Error: Class 'Symfony\Component\Validator\Constraint' not found in C:\Apache24\htdocs\InvoiceTracking\vendor\symfony\validator\Constraints\IsTrue.php:23 Stack trace: #0 {main} thrown in C:\Apache24\htdocs\InvoiceTracking\vendor\symfony\validator\Constraints\IsTrue.php on line 23