Allow <a> and <b> tags in PHP function?

Question

I currently have use this function to clean inputs submitted by users:

// Cleaning input functions
function clean_Input($input) {
    $search = array(
        '@<script[^>]*?>.*?</script>@si', // Strip out javascript
        '@<[\/\!]*?[^<>]*?>@si', // Strip out HTML tags
        '@<style[^>]*?>.*?</style>@siU', // Strip style tags properly
        '@<![\s\S]*?--[ \t\n\r]*>@' // Strip multi-line comments
    );
    $output = preg_replace($search, '', $input);
    return $output;
}

function sanitize($input) {
    if (is_array($input)) {
        foreach ($input as $var => $val) {
            $output[$var] = sanitize($val);
        }
    } else {
        if (get_magic_quotes_gpc()) {
            $input = stripslashes($input);
        }
        $input  = clean_Input($input);
        $output = mysql_real_escape_string($input);
    }
    return $output;
}

However, I want to edit it so that it WILL allow <a> and <b> tags to pass through. Meaning it will accept links and bold tags, and WON'T remove them.

Currently, it removes all HTML tags including <a> tags and <b> tags, how can I change it to accomplish what I stated above?

If I knew how to work with the preg_replace function I would've tried something. However, I'm completely stuck, and have absoultely no idea where to go from here.

Answer 1

Is there anything wrong about using strip_tags, and passing it some tags to allow, and therefore passthrough? Why Regex instead?

Consider the example on the manual page:

$text = '<p>Test paragraph.</p><!-- Comment --> <a href="#fragment">Other text</a>';

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