How to remove multiple UTF-8 BOM sequences

S

12

75

Using PHP5 (cgi) to output template files from the filesystem and having issues spitting out raw HTML.

private function fetch($name) {
    $path = $this->j->config['template_path'] . $name . '.html';
    if (!file_exists($path)) {
        dbgerror('Could not find the template "' . $name . '" in ' . $path);
    }
    $f = fopen($path, 'r');
    $t = fread($f, filesize($path));
    fclose($f);
    if (substr($t, 0, 3) == b'\xef\xbb\xbf') {
        $t = substr($t, 3);
    }
    return $t;
}

Even though I've added the BOM fix I'm still having problems with Firefox accepting it. You can see a live copy here: http://ircb.in/jisti/ (and the template file I threw at http://ircb.in/jisti/home.html if you want to check it out)

Any idea how to fix this? o_o

Shearer answered 24/4, 2012 at 2:4 Comment(2)

utf8 file shouldn't have a BOM, if your editor put those in, there should be a configuration to omit those, if your editor won't allow you to not put in BOM, replace your editor. – Castrato 24/4, 2012 at 2:11

yeah. I use n++, and I tried without BOM – Shearer 28/4, 2012 at 2:17

L

180

you would use the following code to remove utf8 bom

//Remove UTF8 Bom

function remove_utf8_bom($text)
{
    $bom = pack('H*','EFBBBF');
    $text = preg_replace("/^$bom/", '', $text);
    return $text;
}

Laurasia answered 15/3, 2013 at 2:55 Comment(5)

For some reason in the Google+ API, this BOM shows up at the end of the content variable, so I needed to tweak this to remove it from the end of the string. – Anastatius 2/3, 2017 at 18:8

Can someone explain how the pack function is used here? I know it converts a string to a binary representation but struggling to understand how this helps with identifying the BOM Unicode character. – Bittencourt 3/10, 2018 at 6:19

This worked great for my requirement to read the CSV output from SSRS and append to a larger file. – Refuse 20/12, 2018 at 19:28

I used this with trim to cleanse copy/pasted form data like this: $bom = pack('H*','EFBBBF'); $replacementChars = " \n\r\t\v\0" . $bom; $cleanVar = trim($dirtyVar, $replacementChars);. – Irriguous 13/4, 2021 at 14:16

@fsociety The BOM is three bytes - 0xef 0xbb 0xbf. So pack is is using a format of H* which means interpret all values in the string as hexadecimal bytes. I prefer o1max's answer (although has a lower score) that simply uses a string with escape characters:"\xEF\xBB\xBF" – Twayblade 20/4, 2021 at 19:50

S

58

try:

// -------- read the file-content ----
$str = file_get_contents($source_file); 

// -------- remove the utf-8 BOM ----
$str = str_replace("\xEF\xBB\xBF",'',$str); 

// -------- get the Object from JSON ---- 
$obj = json_decode($str);

:)

Shanta answered 18/9, 2013 at 11:19 Comment(0)

A

20

Another way to remove the BOM which is Unicode code point U+FEFF

$str = preg_replace('/\x{FEFF}/u', '', $file);

Arsonist answered 19/6, 2014 at 17:3 Comment(0)

C

8

b'\xef\xbb\xbf' stands for the literal string "\xef\xbb\xbf". If you want to check for a BOM, you need to use double quotes, so the \x sequences are actually interpreted into bytes:

"\xef\xbb\xbf"

Your files also seem to contain a lot more garbage than just a single leading BOM:

$ curl http://ircb.in/jisti/ | xxd

0000000: efbb bfef bbbf efbb bfef bbbf efbb bfef  ................
0000010: bbbf efbb bf3c 2144 4f43 5459 5045 2068  .....<!DOCTYPE h
0000020: 746d 6c3e 0a3c 6874 6d6c 3e0a 3c68 6561  tml>.<html>.<hea
...

Clougher answered 24/4, 2012 at 2:7 Comment(3)

if I was using n++, why would it cause this? it's saving it as unix/utf8 -bom – Shearer 28/4, 2012 at 2:17

Save it as UTF-8 NO BOM (or whatever it's called in N++). – Clougher 28/4, 2012 at 2:26

I did and I'm still getting the same result. I curl'd the direct file (curl ircb.in/jisti/home.html | xxd) and got no leading characters, but curl'ing the PHP script adds the excess data in the front and all I'm using is print to output the data. – Shearer 28/4, 2012 at 2:34

C

6

if anybody using csv import then below code useful

$header = fgetcsv($handle);
foreach($header as $key=> $val) {
     $bom = pack('H*','EFBBBF');
     $val = preg_replace("/^$bom/", '', $val);
     $header[$key] = $val;
}

Camire answered 18/7, 2018 at 6:10 Comment(0)

L

5

This global funtion resolve for UTF-8 system base charset. Tanks!

function prepareCharset($str) {

    // set default encode
    mb_internal_encoding('UTF-8');

    // pre filter
    if (empty($str)) {
        return $str;
    }

    // get charset
    $charset = mb_detect_encoding($str, array('ISO-8859-1', 'UTF-8', 'ASCII'));

    if (stristr($charset, 'utf') || stristr($charset, 'iso')) {
        $str = iconv('ISO-8859-1', 'UTF-8//TRANSLIT', utf8_decode($str));
    } else {
        $str = mb_convert_encoding($str, 'UTF-8', 'UTF-8');
    }

    // remove BOM
    $str = urldecode(str_replace("%C2%81", '', urlencode($str)));

    // prepare string
    return $str;
}

Leesaleese answered 22/6, 2016 at 15:13 Comment(0)

M

4

An extra method to do the same job:

function remove_utf8_bom_head($text) {
    if(substr(bin2hex($text), 0, 6) === 'efbbbf') {
        $text = substr($text, 3);
    }
    return $text;
}

The other methods I found cannot work in my case.

Hope it helps in some special case.

Mytilene answered 7/11, 2016 at 4:53 Comment(0)

D

3

A solution without pack function:

$a = "1";
var_dump($a); // string(4) "1"

function deleteBom($text)
{
    return preg_replace("/^\xEF\xBB\xBF/", '', $text);
}

var_dump(deleteBom($a)); // string(1) "1"

Dewan answered 18/2, 2019 at 9:6 Comment(1)

if they can show up more than once, you might want to use"/^(\xEF\xBB\xBF)+/" – Crepuscule 31/7, 2020 at 21:40

K

2

I'm not so fond of using preg_replace or preg_match for simple tasks. What about this alternative method of detecting and removing the BOM?

function remove_utf8_bom(string $text): string
{
    $bomStart = mb_substr($text, 0, 1);
    return ($bomStart == pack('H*','EFBBBF')) ?
        mb_substr($text, 1) :
        $text;
}

Kraus answered 5/7, 2021 at 8:59 Comment(0)

C

2

How about this:

  function removeUTF8BomHeader($data) {
    if (substr($data, 0, 3) == pack('CCC', 0xef, 0xbb, 0xbf)) {
      $data = substr($data, 3);
    }

    return $data;
  }

tested a lot and it works perfect without any issue

Cyclograph answered 12/11, 2022 at 6:49 Comment(0)

F

1

If you are reading some API using file_get_contents and got an inexplicable NULL from json_decode, check the value of json_last_error(): sometimes the value returned from file_get_contents will have an extraneous BOM that is almost invisible when you inspect the string, but will make json_last_error() to return JSON_ERROR_SYNTAX (4).

>>> $json = file_get_contents("http://api-guiaserv.seade.gov.br/v1/orgao/all");
=> "\t{"orgao":[{"Nome":"Tribunal de Justi\u00e7a","ID_Orgao":"59","Condicao":"1"}, ...]}"
>>> json_decode($json);
=> null
>>>

In this case, check the first 3 bytes - echoing them is not very useful because the BOM is invisible on most settings:

>>> substr($json, 0, 3)
=> "  "
>>> substr($json, 0, 3) == pack('H*','EFBBBF');
=> true
>>>

If the line above returns TRUE for you, then a simple test may fix the problem:

>>> json_decode($json[0] == "{" ? $json : substr($json, 3))
=> {#204
     +"orgao": [
       {#203
         +"Nome": "Tribunal de Justiça",
         +"ID_Orgao": "59",
         +"Condicao": "1",
       },
     ],
     ...
   }

Flowery answered 12/7, 2017 at 17:14 Comment(0)

N

0

When working with faulty software it happens that the BOM part gets multiplied with every saving.

So I am using this to get rid of it.

function remove_utf8_bom($text) {
    $bom = pack('H*','EFBBBF');
    while (preg_match("/^$bom/", $text)) {
        $text = preg_replace("/^$bom/", '', $text);
    }
    return $text;
}

Nutgall answered 9/6, 2019 at 8:49 Comment(0)

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