如何从字符串中删除除反引号中包含的标记之外的所有HTML标记？

Question

I'm using PHP's strip_tags() function to strip tags from a string. For example:

$text = strip_tags( $text );

My aim is to strip all tags unless the tags happen to be contained inside backticks. If tags are contained inside backticks, I don't want to strip them.

My first thought was to try using the second parameter of strip_tags(). This will let me specify allowable tags which are not to be removed. For example, strip_tags( $text, '<strong>'). However, this doesn't quite do what I'm looking for.

How can I strip all HTML tags from a string except tags that happen to be contained inside backticks?

Ref: http://php.net/manual/en/function.strip-tags.php

Answer 1

To back my comment with an answer, something like:

function strip($input)
{
    preg_match_all('/`([^`]+)`/', $input, $retain);

    for($i = 0; $i < count($retain[0]); $i++)
    {
        // Replace HTML wrapped in backticks with match index.
        $input = str_replace($retain[0][$i], "{{$i}}", $input);
    }

    // Strip tags.
    $input = strip_tags($input);

    for($i = 0; $i < count($retain[0]); $i++)
    {
        // Replace previous replacements with relevant data.
        $replace = $retain[1][$i];

        // Do some stuff with $replace here - maybe check that it's a tag
        // you're comfortable with else use htmlspecialchars(), etc.
        // ...

        $input = str_replace("{{$i}}", $replace, $input);
    }

    return $input;
}

With a test:

echo strip("Hello <strong>there</strong>, what's `<em>`up`</em>`?");
// Output: Hello there, what's <em>up</em>?