function strip_html_tags( $text )
{
    $text = preg_replace(
        array(
          // Remove invisible content
            '@<head[^>]*?>.*?</head>@siu',
            '@<style[^>]*?>.*?</style>@siu',
            '@<script[^>]*?.*?</script>@siu',
            '@<object[^>]*?.*?</object>@siu',
            '@<embed[^>]*?.*?</embed>@siu',
            '@<applet[^>]*?.*?</applet>@siu',
            '@<noframes[^>]*?.*?</noframes>@siu',
            '@<noscript[^>]*?.*?</noscript>@siu',
            '@<noembed[^>]*?.*?</noembed>@siu',
          // Add line breaks before and after blocks
            '@</?((address)|(blockquote)|(center)|(del))@iu',
            '@</?((div)|(h[1-9])|(ins)|(isindex)|(p)|(pre))@iu',
            '@</?((dir)|(dl)|(dt)|(dd)|(li)|(menu)|(ol)|(ul))@iu',
            '@</?((table)|(th)|(td)|(caption))@iu',
            '@</?((form)|(button)|(fieldset)|(legend)|(input))@iu',
            '@</?((label)|(select)|(optgroup)|(option)|(textarea))@iu',
            '@</?((frameset)|(frame)|(iframe))@iu',
        ),
        array(
            ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' ',
            "
$0", "
$0", "
$0", "
$0", "
$0", "
$0",
            "
$0", "
$0",
        ),
        $text );
 
    // you can exclude some html tags here, in this case B and A tags       
    return strip_tags( $text , '<b><a>' );
}

strip_tags is a default HTML Tag stripper in PHP. However, it can't strip some of the tags, so this enhanced version called strip_html_tags will remove more html elements.

Strip HTML Tags Function for PHP

PHP