编码-截取中文-去除HTML字符

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

<?php

header('Content-Type: text/html; charset=utf-8');

function content_replace($show_content){
     $search = array(
        "'<script[^>]*?>.*?</script>'si", //过滤SCRIPT标记
        "'<iframe[^>]*?>.*?</iframe>'si", //过滤IFRAME标记
        "'<style[^>]*?>.*?</style>'si", //过滤STYLE标记
        "'<[\/\!]*span[^<>]*?>'si", //过滤SPAN标记
        "'<[\/\!]*strong[^<>]*?>'si", 
        "'<[\/\!]*span[^<]*?>'si", //过滤SPAN标记
        "'<[\/\!]*br[^<>]*?>'si", //过滤br标记
        "'<[\/\!]*img[^<>]*?>'si", //过滤img标记
        "'<[\/\!]*input[^<>]*?>'si", //过滤input标记
        "'<[\/\!]*font[^<>]*?>'si", //过滤FONT标记
        "'<[\/\!]*textarea[^<>]*?>'si", //过滤textarea标记
        "'<[\/\!]*form[^<>]*?>'si", //过滤form标记
        "'<[\/\!]*a[^<>]*?>'si", //过滤A标记,如果要过滤链接中的字，必须在过滤规则中写下。
        "'<[\/\!]*div[^<>]*?>'si", //过滤DIV标记
        "'<[\/\!]*tbody[^<>]*?>'si", //过滤TABLE标记
        "'<[\/\!]*table[^<>]*?>'si", //过滤TABLE标记
        "'<[\/\!]*tr[^<>]*?>'si", //过滤TABLE标记
        "'<[\/\!]*td[^<>]*?>'si", //过滤TABLE标记
        "'<[\/\!]*p[^<>]*?>'si", //过滤P标记
        "'<[\/\!]*o:p[^<>]*?>'si", //过滤o:p标记
        "'<[\?\!]*xml:[^<>]*?>'si", //过滤xml:标记
        "'<[\/\!]*select[^<>]*?>'si", //过滤select标记
        "'<[\/\!]*option[^<>]*?>'si", //过滤option标记
        "'<[\/\!]*v:[^<>]*?>'si", //过滤v:标记
        "'<[\/\!]*o:[^<>]*?>'si", //过滤o:标记
        "'target=([^\s>]*)|method=([^\s>]*)|action=([^\s>]*)|rows=([^\s>]*)|cols=([^\s>]*)|type=([^\s>]*)|href=([^\s>]*)|src=([^\s>]*)|id=([^\s>]*)|class=([^\s>]*)|name=([^\s>]*)|align=([^\s>]*)|cellpadding=([^\s>]*)|cellspacing=([^\s>]*)|border=([^\s>]*)|bordercolor=([^\s>]*)|background=([^\s>]*)|bgcolor=([^\s>]*)'si",
        "'&#(\d+);'e",
    );

    $replace = array("", "", "", "", "", "", "", "", "", "", "", "", "", "", "", "","", "", "", "", "chr(\\1)");
    $show_content = preg_replace($search, $replace, $show_content);
    $show_content = preg_replace("/style=['\"]*([^'\"]*)['\"]*/is", "", $show_content);
    $show_content = str_replace("\r\n", "", $show_content); //去除HTML中的换行符&nbsp;
    $show_content = str_replace("<span", "", $show_content); //去除HTML中的换行符&nbsp;
    $show_content = str_replace("&nbsp;", "", $show_content); //去除HTML中的换行符
    $show_content = str_replace(" ", "", $show_content); //去除HTML中的换行符
    return $show_content;   
}

//中文字符截取函数
function cnsubstr($string, $sublen ,$a=0){
    if ($string == ''){
        return false;
    }
    $string = changeYinhaoCom($string,'out');
    $sum = 0;
    for ($i = 0 ; $i < strlen($string) ; $i++){
        if(ord($string{$i}) > 127) {
            $s .= $string{$i} . $string{++$i} . $string{++$i};
            $sum++;
            continue;
        } else {
            $s .= $string{$i};
            $sum++;
            continue;
        }
    }
    if($sublen >= $sum) {
        return $string;
    }
    $s = "";
    $index = 0;
    for($i = 0; $i < $sublen; $i++) {
        if(ord($string{$index}) > 127) {
            $s .= $string{$index} . $string{++$index} . $string{++$index};
            $index++;
            continue;
        } else {
            $s .= $string{$index};
            $index++;
            continue;
        }
    }
    if($a===0){
        $s.="...";
    }else{
        $s.=$a;
    }
    return $s;
}
function changeYinhaoCom($content , $flag){
    if($flag=="in"){
        $content  = str_replace("\"","&quot;",$content);
        $content  = str_replace("'","'",$content);
    }
    if($flag=="out"){
        $content  = str_replace("&quot;","\"",$content);
        $content  = str_replace("'","'",$content);
    }
    return $content;
}

//调用方法
$str = '这是一段很长的字符串我要把它截取一部分';
echo cnsubstr(content_replace($str),5);
echo $res;