php过滤掉无法识别的问号字符解决方案

$str = file_get_contents('example_text.txt');<br />echo $str;

<br />function filter_utf8_char($ostr){<br />    preg_match_all('/[\x{FF00}-\x{FFEF}<br><font color='#FF8000'>------解决方案--------------------</font><br>\x{0000}-\x{00ff}<br><font color='#FF8000'>------解决方案--------------------</font><br>\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}<br><font color='#FF8000'>------解决方案--------------------</font><br>\x{0000}-\x{00ff}<br><font color='#FF8000'>------解决方案--------------------</font><br>\x{4e00}-\x{9fff}]+/u', $str, $matches);<br />        $str = join('', $matches[0]);<br />    }<br />    return $str;<br />}<br />