FPDF错误：某些数据已经输出，无法发送PDF文件

Question

well I get this error trying to use php class FPDF:

FPDF error: Some data has already been output, can't send PDF file (output started at
/mnt/webc/e1/12/5691512/htdocs/adminpanel/fpdf/test.php:1)

My test.php

<?php
require_once("fpdf.php");
$pdf = new FPDF();
$pdf->AddPage();
$pdf->SetFont('Arial','B',16);
$pdf->Cell(40,10,'Hello World!');
$pdf->Output();
?>

There are no blanks or anything... So where is the error???

Answer 1

Some editors adds BOM at the start of a file.

View your file in hex and remove it