Search Canonical Push for Google Analytics

search-canonical-push-for-ga.php

<?php
/**
 * Plugin Name: Search Canonical Push for Google Analytics
 * Plugin URI: https://theseoframework.com/
 * Description: This plugin adds a small script to Search archives that optimizes the Google Analytics script when using pretty Search links.
 * Version: 1.0.1
 * Author: Sybre Waaijer
 * Author URI: https://theseoframework.com/
 * License: GPLv3
 */

/**
 * Search Canonical Push for Google Analytics
 * Copyright (C) 2017 Sybre Waaijer, CyberWire (https://cyberwire.nl/)
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * Generates a script that is injected very early.
 * It adjusts the Google Analytics 'send' script to believe there's a search parameter.
 * This will allow Google Analytics users to capture and analyze site search queries.
 *
 * This script will listen to DOMnode insertion changes, and will overwrite the
 * 'send' function of Google Analytics when found.
 * That adjustment forces an extra parameter to comply to the search results, when
 * possible.
 *
 * After it's done, it will stop listening.
 *
 * @since 1.0.0
 * @return void
 */
\add_action( 'wp_head', function() {

	if ( ! \is_search() || empty( $GLOBALS['wp_rewrite']->get_search_permastruct() ) )
		return;

	$q = \get_search_query();
	$lr = \set_url_scheme( \get_search_link( $q ), 'relative' );
	$s_ga_lr = \esc_js( $lr . '?s=' . urlencode( $q ) );

	//= Already escaped.
	echo <<<GAFIX
<script>document.addEventListener("DOMNodeInserted",function a(){if("ga"in window){var b=window.ga;window.ga=function(){3>arguments.length&&"send"===arguments[0]&&"pageview"===arguments[1]&&[].push.call(arguments,"$s_ga_lr");b.apply(function(){},arguments)};document.removeEventListener("DOMNodeInserted",a)}});</script>\n
GAFIX;
}, ~ PHP_INT_MAX );

/*== Javascript source ==

document.addEventListener( 'DOMNodeInserted', function a() {
	if ( ! ( 'ga' in window ) ) return;

	var originalMethod = window['ga'];
	window['ga'] = function () {
		if ( arguments.length < 3 ) {
			if ( 'send' === arguments[0] && 'pageview' === arguments[1] ) {
				[].push.call( arguments, "$s_ga_lr" );
			}
		}
		originalMethod.apply( function() {}, arguments );
	};
	document.removeEventListener( 'DOMNodeInserted', a );
} );

==/ Javascript source ==*/

Tested for two weeks. GA doesn't seem to interpret the data.
I will look at this today.

Edit: The previous version assumed the wrong method. It should work now.

I forgot to mention: this snippet requires PHP 5.5 or later.