Highlight Search Terms for WordPress

Very lightweight (vanilla) Javascript that wraps search terms in an HTML5 mark tag within WordPress search results.

Description

Highlights search terms within WordPress generated search results, both on the search results page and on each linked post page itself.

This plugin is light weight and has no options. It started as very simple fusion between How to Highlight Search Terms with jQuery – theme hack by Thaya Kareeson and Search Hilite by Ryan Boren. It has since evolved with many optimizations, HTML5 and bbPress support.

Since version 1.6 it no longer depends on the jQuery library.

Features

• Click through highlights: Highlights not only on WP search results page but also one click deeper inside any of the found pages
• Character and case insensitive (lenient) highlighting
• BuddyPress / bbPress compatibility: highlighting within forum searches
• Caching (WP Super Cache) compatibility
• Search terms wrapped in double quotes now considered as single term

What does it do?

This low impact plugin finds all search terms on a search results page inside each post and highlights them with a <mark class="hilite term-N"> ... </mark> tag.
Note that N is a number starting with 0 for the first term used in the search phrase increasing 1 for each additional term used. Any part of a search phrase wrapped in quotes is considered as a single term.

What does it NOT do?

There are no CSS style rules set for highlighting. You are free to use any styling you wish but to make the highlights visible in browsers that do not support HTML5 like Internet Explorer 8 or older you absolutely need to define at least one rule.
Modern HTML5 browsers will use their own highlighting style by default, which usually is a yellow marker style background.

So what do I need to do?

In most cases, it should just work. But you can do two things to ensure backward browser and theme compatibility:

1. Define CSS rules: There are no configuration options and there is no predefined highlight styling. You are completely free to define any CSS styling rules in your themes main stylesheet (style.css) or the Custom CSS tab if the WordPress theme customizer.
   You can find basic instructions and CSS examples in the FAQ’s.
2. Check your theme: In most up to date themes (including WP’s own default theme) post and page content is shown inside a div with class hentry. This means search terms found in post and page content will be highlighted but not similar terms that accidentally show in the page header, sidebar or footer.
   If your current theme does not use the hentry class (yet), this plugin will look for IDs content, main and finally wrapper but if none of those are found, it will not work for you out of the box. See the last of the FAQ’s for ways to make it work.

Available hooks and filters

1. hlst_query_vars – The array of WordPress query variables that the plugin will identify as a search query. Must return an array. Default: ['search_terms','bbp_search'] (WordPress abd bbPress search)
2. hlst_input_get_args – An array of GET variables that the plugin will identify as a search query. Must return an array. Default: ['hilite'] (for click-through highlighting)
3. hlst_selectors – The array of possible HTML DOM element identifiers that the script will try. The first viable identifier it finds elements of will be scanned for search terms to mark, the rest is ignored. So the order is important here! Start with the element closest to, but still containing all the post/page title, excerpt or content.
4. hlst_events – The array of DOM event listeners that the inline script will watch for. Default: ['DOMContentLoaded','post-load'] (on Document Ready and for Jetpack Infinite Scroll and others).
5. hlst_inline_script – The inline script that will be added to the plugin script file. Can be used to add to or alter the inline script. Must return a string.

Known issues & development

1. If your theme does not wrap the main content section of your pages in a div with class “hentry” or HTML5 article tags, this plugin might not work well for you out of the box. However, you can make it work. See the last of the FAQ’s for an explanation.
2. Josh pointed out a conflict with the ShareThis buttons plugin. Since then, that plugin has been completely rewriten so please let me know if the problem still exists. Thanks!
3. When search engine referrer is using SSL (notice the https:// in the URL) then the search terms cannot be determined. Most search engines are always over SSL nowadays. There is no way to get around that issue.

Please file bug reports and code contributions as pull requests on GitHub.

Installation instructions

To make it work, you will need to take up to three steps, depending on your wishes and WordPress theme. (I) A normal installation and activation procedure; (II) Make sure your theme uses any of the recognized classes or ID’s for the post content div so that the script knows where and where not to look for search terms;
and (III) optionally add CSS styling rules to get highlighting for older browsers that do not support HTML5 like Internet Explorer 8 and below.

I. Install now or use the slick search and install feature (Plugins > Add New and search for “highlight search terms”) in your WP2.7+ admin section or follow these basic steps.

1. Download archive and unpack.
2. Upload (and overwrite) the /highlight-search-terms/ folder and its content to the /plugins/ folder.
3. Activate plugin on the Plug-ins page

II. In most up to date themes (including WP’s own Default theme) post and page content is shown inside an ARTICLE element or DIV with class hentry.
This is recognized by the hilite script, which means search terms found in post and page content will be highlighted but not similar terms that coincidentally reside in the page header, menu, sidebar or footer.

If your current theme does not use these common designations (yet), this plugin will look for some other possible tags like #content, MAIN, #wrapper (which might include the header, sidebar and footer areas) and finally the BODY.

If this causes issues on your theme, see the last of the FAQ’s for ways to make it work.

III. Optionally add at least one new rule to your themes stylesheet or the Custom CSS editor to style highlightable text.

For example use .hilite { background:#D3E18A; } to get a moss green background on search terms found in the content section (not header, sidebar or footer; assuming your Theme uses a div with class “hentry”).

Please find more examples in the FAQ’s.

Frequently Asked Questions

.hilite {
    background-color: #D3E18A;
}

.hilite {
    background-color: yellow;
}

.hilite {
    background-color: #9CD4FF;
    font-weight:bold;
}

.hilite {
    background-color: #FFCA61;
    color: #000000;
}

/* Default highlighting, but bold text. */
.hilite {
    background-color: yellow;
    font-weight: bold;
}
/* Moss green highlighting for second search term only. */
.term-1 {
    background-color: #D3E18A;
}
/* Light blue highlighting for third search term only. */
.term-2 {
    background-color: #9CD4FF;
}
/* Orange highlighting for fourth search term only. */ 
.term-3 {
    background-color:#FFCA61
}

add_filter(
    'hlst_selectors',
    function( $selectors ) {
        // custom theme selectors (change and append as needed)
        $my_selectors = array(
            'div.someclass'
        );
        return $my_selectors + (array) $selectors;
    }
);