Notice: A session had already been started - ignoring session_start() in C:\xampp\htdocs\costprev\pdf\invoice.php on line 3

Notice: Undefined index: codigo_proyecto in C:\xampp\htdocs\costprev\sql\funciones3.php on line 6

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Fatal error: Uncaught exception 'Exception' with message 'FPDF error: Some data has already been output, can't send PDF file' in C:\xampp\htdocs\costprev\pdf\pdf\fpdf.php:271 Stack trace: #0 C:\xampp\htdocs\costprev\pdf\pdf\fpdf.php(1063): FPDF->Error('Some data has a...') #1 C:\xampp\htdocs\costprev\pdf\pdf\fpdf.php(999): FPDF->_checkoutput() #2 C:\xampp\htdocs\costprev\pdf\invoice.php(64): FPDF->Output() #3 C:\xampp\htdocs\costprev\pdf\generador_invoice.php(3): require_once('C:\\xampp\\htdocs...') #4 {main} thrown in C:\xampp\htdocs\costprev\pdf\pdf\fpdf.php on line 271