phpは認識できない疑問符文字を除外します

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function filter_utf8_char($ostr){<br />
    preg_match_all('/[\x{FF00}-\x{FFEF}\x{0000}-\x{00ff}\x{4e00}-\x{9fff}]+/u', $ostr, $matches);<br />
    $str = join('', $matches[0]);<br />
    if($str==''){   //含有特殊字符需要逐個處理<br />
        $returnstr = '';<br />
        $i = 0;<br />
        $str_length = strlen($ostr);<br />
        while ($i<=$str_length){<br />
            $temp_str = substr($ostr, $i, 1);<br />
            $ascnum = Ord($temp_str);<br />
            if ($ascnum>=224){<br />
                $returnstr = $returnstr.substr($ostr, $i, 3);<br />
                $i = $i + 3;<br />
            }elseif ($ascnum>=192){<br />
                $returnstr = $returnstr.substr($ostr, $i, 2);<br />
                $i = $i + 2;<br />
            }elseif ($ascnum>=65 && $ascnum<=90){<br />
                $returnstr = $returnstr.substr($ostr, $i, 1);<br />
                $i = $i + 1;<br />
            }elseif ($ascnum>=128 && $ascnum<=191){ // 特殊字符<br />
                $i = $i + 1;<br />
            }else{<br />
                $returnstr = $returnstr.substr($ostr, $i, 1);<br />
                $i = $i + 1;<br />
            }<br />
        }<br />
        $str = $returnstr;<br />
        preg_match_all('/[\x{FF00}-\x{FFEF}\x{4e00}-\x{9fff}]+/u', $str, $matches);<br />
        $str = join('', $matches[0]);<br />
    }<br />
    return $str;<br />
}<br />