Auto-tag Amazon.com links (v1: Raw)

auto-tag-amazon-links-v1.php

<?php
/**
 * Auto-tag Amazon.com links (v1: Raw)
 * 
 */
add_filter( 'the_content', 'ac_auto_tag_amazon_links_v1' );

function ac_auto_tag_amazon_links_v1( $content ) {

	// Variables
	$amazon_tag = array( 'tag' => 'adamcapr-20', ); // Update with your tracking ID

	// Add "tag" parameter to Amazon URLs, replacing existing "tag" parameter if present
	$search = '/a href="(https?:\/\/(?:www)?\.amazon\.com[^"]*)"/';
	$replace = 'a href="' . add_query_arg( $amazon_tag, "$1" ) . '"'; // esc_url *should* be used here, but it breaks the URLs for some reason; would need to run second replacement afterward to catch malformed instances of https// and http//
	$content = preg_replace( $search, $replace, $content );

	return $content;

}