Encoding a string as UTF-8 with BOM in PHP

Question

how can I force PHP to add the BOM when using utf8_encode ?

Here's what I am trying to do:

$zip->addFromString($filename, utf8_encode($xml));

Unfortunately (for me), the result will not have the BOM mark at the beginning.

Solution

Have you tried adding one yourself?

The UTF-8 BOM seems to be 0xEF 0xBB 0xBF, so you can attach it to your string after conversion to UTF-8.

$utf8_with_bom = chr(239) . chr(187) . chr(191) . $utf8_string;

Watch out, though. utf8_encode wants an ISO-8859-1 string. If you're working with XML, make sure that the XML isn't already UTF-8 encoded. The comments on the documentation suggest that the function is broken in a variety of fun ways, so you shouldn't throw it around unless you know that you need it.

Remember, PHP strings are simply dumb, unknowing bytes. They don't have a character set attached to them, so if the data in the string is already UTF-8, you don't need to run the conversion.

Also, the linked Wikipedia article says this:

While Unicode standard allows BOM in UTF-8, it does not require or recommend it. Byte order has no meaning in UTF-8 so a BOM only serves to identify a text stream or file as UTF-8 or that it was converted from another format that has a BOM.

You probably don't need to bother with the BOM tapdance to begin with.

Comments

[OrganicPanda]

I had a problem where Excel wouldn't open my UTF-8 CSV correctly without the BOM so it may not be required but it certainly can make a difference.

[Niet the Dark Absol]

You can make the number seem less "magical" by doing chr(0xEF).chr(0xBB).chr(0xBF) - this way you can see that it's hex, and from there understand better that it's the BOM.

[Scott Chu]

If you use some old editor, e.g. EditPlus, then 'find in file' function can only search and recognize file with foreign characters encoded in utf8+bom.

[Luka Ramishvili]

Keep in mind that for the .CSV file to work in Excel for Mac, UTF8 BOM and encoding won't work - you need to convert your data to UTF16-LE and add a UTF16-LE BOM - stackoverflow.com/a/16766198/324220

[Kenny Wyland]

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