"UTF-8 BOM Header information Output" What does that mean? How to deal with it

"UTF-8 BOM Header information Output" What do you mean by this sentence?
"UTF-8 BOM Header information Output" What do you mean by this sentence?

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The UTF-8 encoded header will have two special characters by default, and these two special characters are the BOM
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Take a look at this explanation:
Http://hi.baidu.com/%CE%D2%B5%C4%B5%C6%C5%DD%C1%C1%C1%CB/blog/item/9c1660ee5db2b03cadafd5e7.html
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I remember PHP if saved as UTF-8 BOM format, the top of the page will be a line of empty lines (at least I was under IE8)
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So you're going to love notepad++.
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When saving the utf-8php file, it is best not to save it in UTF-8 BOM header mode.
Otherwise, you will get an error in the program, using Session,header, and compressing the output.
The BOM header is just a file identifier that is added to the beginning of the file. It is invisible with an ordinary editor, but it does exist and will be output at the outset. It's because it's in the head, and it starts out, it causes the use of Session,header, and when the output is compressed, an error occurs.

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