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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 /var/www/html/fpdf.php:271 Stack trace: #0 /var/www/html/fpdf.php(1063): FPDF->Error('Some data has a...') #1 /var/www/html/fpdf.php(999): FPDF->_checkoutput() #2 /var/www/html/pdf-generator.php(401): FPDF->Output('sample chapter ...', 'I') #3 {main} thrown in /var/www/html/fpdf.php on line 271