UTF-8 BOM signature in PHP files

Question

I was writing some commented PHP classes and I stumbled upon a problem. My name (for the @author tag) ends up with a ș (which is a UTF-8 character, ...and a strange name, I know).

Even though I save the file as UTF-8, some friends reported that they see that character totally messed up (È™). This problem goes away by adding the BOM signature. But that thing troubles me a bit, since I don't know that much about it, except from what I saw on Wikipedia and on some other similar questions here on SO.

I know that it adds some things at the beginning of the file, and from what I understood it's not that bad, but I'm concerned because the only problematic scenarios I read about involved PHP files. And since I'm writing PHP classes to share them, being 100% compatible is more important than having my name in the comments.

But I'm trying to understand the implications, should I use it without worrying? or are there cases when it might cause damage? When?

Answer 1

Indeed, the BOM is actual data sent to the browser. The browser will happily ignore it, but still you cannot send headers then.

I believe the problem really is your and your friend's editor settings. Without a BOM, your friend's editor may not automatically recognize the file as UTF-8. He can try to set up his editor such that the editor expects a file to be in UTF-8 (if you use a real IDE such as NetBeans, then this can even be made a project setting that you can transfer along with the code).

An alternative is to try some tricks: some editors try to determine the encoding using some heuristics based on the entered text. You could try to start each file with

<?php //Úτƒ-8 encoded

and maybe the heuristic will get it. There's probably better stuff to put there, and you can either google for what kind of encoding detection heuristics are common, or just try some out :-)

All in all, I recommend just fixing the editor settings.

Oh wait, I misread the last part: for spreading the code to anywhere, I guess you're safest just making all files only contain the lower 7-bit characters, i.e. plain ASCII, or to just accept that some people with ancient editors see your name written funny. There is no fail-safe way. The BOM is definitely bad because of the headers already sent thing. On the other side, as long as you only put UTF-8 characters in comments and so, the only impact of some editor misunderstanding the encoding is weird characters. I'd go for correctly spelling your name and adding a comment targeted at heuristics so that most editors will get it, but there will always be people who'll see bogus chars instead.

Answer 2

BOM would cause Headers already sent error, so, you can't use BOM in PHP files

Answer 3

This is an old post and have already been answered, but i can leave you some others resources that i found when i faced with this BOM issue.

http://people.w3.org/rishida/utils/bomtester/index.php with this page you can check if a specific file contains BOM.

There is also a handy script that outputs all files with BOM on your current directory.

<?php 
function fopen_utf8 ($filename) { 
    $file = @fopen($filename, "r"); 
    $bom = fread($file, 3); 
    if ($bom != b"\xEF\xBB\xBF") 
    { 
        return false; 
    } 
    else 
    { 
        return true; 
    } 
} 

function file_array($path, $exclude = ".|..|design", $recursive = true) { 
    $path = rtrim($path, "/") . "/"; 
    $folder_handle = opendir($path); 
    $exclude_array = explode("|", $exclude); 
    $result = array(); 
    while(false !== ($filename = readdir($folder_handle))) { 
        if(!in_array(strtolower($filename), $exclude_array)) { 
            if(is_dir($path . $filename . "/")) { 
                                // Need to include full "path" or it's an infinite loop 
                if($recursive) $result[] = file_array($path . $filename . "/", $exclude, true); 
            } else { 
                if ( fopen_utf8($path . $filename) ) 
                { 
                    //$result[] = $filename; 
                    echo ($path . $filename . "<br>"); 
                } 
            } 
        } 
    } 
    return $result; 
} 

$files = file_array("."); 
?>

I found that code at php.net

Dreamweaver also helps with this, it gives you the option to save the file and not include the BOM stuff

Its a late answer, but i still hope it helps. Bye

Answer 4

Just so you know, there's an option in php, zend.multibyte, which allows php to read files with BOM without giving the Headers already sent error.

From the php.ini file:

; If enabled, scripts may be written in encodings that are incompatible with
; the scanner.  CP936, Big5, CP949 and Shift_JIS are the examples of such
; encodings.  To use this feature, mbstring extension must be enabled.
; Default: Off
;zend.multibyte = Off

Answer 5

Or you could activate output buffering in php.ini which will solve the "headers already sent" problem. It is also very important to use output buffering for performance if your site has significant load.

Answer 6

In PHP, in addition to the "headers already sent" error, the presence of a BOM can also screw up the HTML in the browser in more subtle ways.

See this link for an outline of the problem.

When this occurs, not only is there usually a noticeable space at the top of the rendered page, but if you inspect the HTML in Firefox or Chrome, you may notice that the head section is empty and its elements appear to be in the body. Of course viewing source will show everything where it should be, but somehow the browser is interpreting it wrong.

Answer 7

BOM is actually the most efficient way of identifying an UTF-8 file, and both modern browsers and standards support and encourage the use of it in HTTP response bodies.

In case of PHP files its not the file but the generated output that gets sent as response so obviously it's not a good idea to save all PHP files with the BOM at the beginning, but it doesn't mean you shouldn't use the BOM in your response.

You can in fact safely inject the following code right before your doctype declaration (in case you are generating HTML as response):

<?="\xEF\xBB\xBF"?>

For further read: https://www.w3.org/International/questions/qa-byte-order-mark#transcoding