Convert 2 similarly-looking German characters of d

Question

I have these two strings:

$str1 = 'Ö';
$str2 = 'Ö';
$e1 = mb_detect_encoding($str1);
$e2 = mb_detect_encoding($str2);
var_dump($str1);
var_dump($str2);
echo 'e1: '.$e1.', e2: '.$e2;

the result is:

string(3) "Ö"
string(2) "Ö"
e1: UTF-8, e2: UTF-8

It seems that they are not only German characters but also each of them is different so converting them to ASCII this way

PHP: Replace umlauts with closest 7-bit ASCII equivalent in an UTF-8 string

doesn't produce equal results. Is there a way to convert both of these strings to one of these ASCII forms BNOE or BNO?

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I know that maybe I could copy Ö from both and include in strtr search and replace array but I don't know how to reproduce all the charactes encoded the same way the first Ös are.

Answer 1

These are two different forms to express the same letter in Unicode; one is the combination of an O with combining diereses, the other is the letter Ö. Unicode allows either variant to express "Ö".

To normalize that into your preferred variant, use Normalizer::normalize:

$str = Normalizer::normalize('Ö', Normalizer::FORM_C);

Likely you want Form C, which will converge on "Ö" (the single letter form). If you prefer "O" + combining diereses, use Form D instead.

Answer 2

Extending Andreas's answer. These characters are letter + combining diaeresis(U-0308). I was able to search and replace them to standard umlauts, then replace with whatever is needed. This is the fuction I've used to replace them:

function convertToUmlauts($str) {
    $srp_array = ['Ö' => 'Ö', 'Ä' => 'Ä', 'Ü' => 'Ü', '̈a' => 'ä', 'ö' => 'ö', 'ü' => 'ü'];
    return strtr($str, $srp_array);
}

Answer 3

You could first convert your input to utf-8 using iconv and then apply your conversion to ASCII. To detect the current encoding you can use mb_detect_encoding.

$aUTF8 = iconv(mb_detect_encoding($a, 'UTF-8, ISO-8859-1', true), 'UTF-8', $a);
$bUTF8 = iconv(mb_detect_encoding($b, 'UTF-8, ISO-8859-1', true), 'UTF-8', $b);

$aASCII = iconv("utf-8", "ascii//TRANSLIT", $aUTF8);
$bASCII = iconv("utf-8", "ascii//TRANSLIT", $bUTF8);

Please note that you might have to add additional encodings to the encoding list of mb_detect_encoding.