php 批量替换html标签

1.把html元素全部去掉，或者保留某几个html标签

<?php
$text = "<p>Test paragraph.</p><!-- Comment --> <a href="#fragment">Other text</a>";
echo strip_tags($text);
echo "/n";

// Allow <p> and <a>
echo strip_tags($text, "<p><a>");
?>

结果为(去掉了注释)：

<blockquote>Test paragraph. Other text
<p>Test paragraph.</p> <a href="#fragment">Other text</a></blockquote>

2.相反，只去掉某一个html标签

<?php
function strip_only($str, $tags, $stripContent = false) {
    $content = "";
    if(!is_array($tags)) {
        $tags = (strpos($str, ">") !== false ? explode(">", str_replace("<", "", $tags)) : array($tags));
        if(end($tags) == "") array_pop($tags);
    }
    foreach($tags as $tag) {
        if ($stripContent)
             $content = "(.+</".$tag."[^>]*>|)";
         $str = preg_replace("#</?".$tag."[^>]*>".$content."#is", "", $str);
    }
    return $str;
}

$str = "<font color="red">red</font> text";
$tags = "font";
$a = strip_only($str, $tags); // red text
$b = strip_only($str, $tags, true); // text
?>