Need help with a function - Urgent

Question

In the file qa-include/util/string.php there is this function:

function qa_string_to_words($string, $tolowercase = true, $delimiters = false, $splitideographs = true, $splithyphens = true)
{
    if (qa_to_override(__FUNCTION__)) { $args=func_get_args(); return qa_call_override(__FUNCTION__, $args); }

    global $qa_utf8punctuation;

    if ($tolowercase)
        $string = qa_strtolower($string);

    $string = strtr($string, $qa_utf8punctuation);

    $separator = QA_PREG_INDEX_WORD_SEPARATOR;
    if ($splithyphens)
        $separator .= '|\-';

    if ($delimiters) {
        if ($splitideographs)
            $separator .= '|' . QA_PREG_CJK_IDEOGRAPHS_UTF8;

    } else {
        $string = preg_replace("/(\S)'(\S)/", '\1\2', $string); // remove apostrophes in words

        if ($splitideographs) // put spaces around CJK ideographs so they're treated as separate words
            $string = preg_replace('/' . QA_PREG_CJK_IDEOGRAPHS_UTF8 . '/', ' \0 ', $string);
    }

    return preg_split('/(' . $separator . '+)/', $string, -1, PREG_SPLIT_NO_EMPTY | ($delimiters ? PREG_SPLIT_DELIM_CAPTURE : 0));
}

 How can i create a new function for letters/characters instead of words. I want a new function like: 

function qa_string_to_letters($string, $tolowercase = true, $delimiters = false, $splitideographs = true, $splithyphens = true)
 

I hope that someone of the developer like Puppi, Scott or anyone else could help me with this. Thanks everybody.

Comments

Splitting a string into characters is relatively simple: $char_array = str_split($string).

Howevre, I have a feeling this might be an X-Y question, so please take a step back and describe the actual problem you're trying to solve instead of what you perceive as the solution. What do you need this function for?

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Thank you Ansgar. Your comment is helpful
 I ll let you know if I need further assistance. Cheers