gistfile1.php

<?php
if(!function_exists('mb_ucfirst')) {
    function mb_ucfirst($str, $enc = 'UTF-8') {
        return Wader\Mbstring::ucfirst($str, $enc);
    }
}
if(!function_exists('mb_lcfirst')) {
    function mb_lcfirst($str, $enc = 'UTF-8') {
        return Wader\Mbstring::lcfirst($str, $enc);
    }
}
if(!function_exists('mb_str_replace')){
    function mb_str_replace($search, $replace, $subject, &$count = 0){
        return Wader\Mbstring::str_replace($search, $replace, $subject,$count);
    }
}

if(!function_exists('mb_ucwords')){
    function mb_ucwords($word){
        return Wader\Mbstring::ucwords($word);
    }
}

Mbstring.php

<?php

namespace Wader;

final class Mbstring {
    /**
     * upcase first char in string
     * @param string $str
     * @return string
     */
    public static function ucfirst($string, $enc = 'UTF-8'){
        return mb_convert_case(mb_substr($string,0,1), MB_CASE_UPPER, $enc).
            mb_substr($string, 1, mb_strlen($string, $enc), $enc);
    }

    /**
     * lowcase first char in string
     * @param string $str
     * @return string
     */
    public static function lcfirst($string, $enc = 'UTF-8'){
        return mb_convert_case(mb_substr($string,0,1), MB_CASE_LOWER, $enc).
            mb_substr($string, 1, mb_strlen($string, $enc), $enc);
    }

    public static function ucwords($word){
        return mb_convert_case($word,MB_CASE_TITLE);
    }

    public static function str_replace($search, $replace, $subject, &$count = 0){
        if (!is_array($subject)){
            $searches = is_array($search) ? array_values($search) : array($search);
            $replacements = is_array($replace) ? array_values($replace) : array($replace);
            $replacements = array_pad($replacements, count($searches), '');
            foreach ($searches as $key => $search){
               $parts = mb_split(preg_quote($search), $subject);
               $count += count($parts) - 1;
               $subject = implode($replacements[$key], $parts);
            }
        }else{
           foreach ($subject as $key => $value){
                $subject[$key] = self::str_replace($search, $replace, $value, $count);
           }
        }

        return $subject;
    }
}