How to remove multiple UTF-8 BOM sequences

StackOverflow https://stackoverflow.com/questions/10290849

  •  02-06-2021
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Question

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

Was it helpful?

Solution

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;
}

OTHER TIPS

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);

:)

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

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

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
...

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;
}

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;
}

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"

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.

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",
       },
     ],
     ...
   }

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;
}

This might help. let me know if you care for me to expand my thought process.

<?php
    //
    // labled TESTINGSTRIPZ.php
    //

    define('CHARSET', 'UTF-8');

    $stringy = "\xef\xbb\xbf\"quoted text\" ";
    $str_find_array    = array( "\xef\xbb\xbf");
    $str_replace_array = array(             '');


    $RESULT =
        trim(
            mb_convert_encoding(

                str_replace(
                    $str_find_array,
                    $str_replace_array,
                    strip_tags( $stringy )
                    ),

                'UTF-8',

                mb_detect_encoding(
                    strip_tags($stringy)
                    )

                )
            );

        print("YOUR RESULT IS: " . $RESULT.PHP_EOL);

?>

Result:

terminal$ php TESTINGSTRIPZ.php 
      YOUR RESULT IS: "quoted text" // < with no hidden char.
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