WordPress Transients Tutorial, Part 2

wordpress-transients-tutorial-02.php

<?php
/**
 * Get Books posts.
 *
 * This is from a tutorial found here:
 * @link https://johnregan3.wordpress.com/how-to-improve-wordpress-load-times-using-transients
 *
 * @since 1.0.0
 *
 * @param array $genre_array An array of genre slugs.
 * @param array $publisher_array An array of publisher slugs.
 *
 * @return array Array of books, else an empty array.
 */
function jr3_get_books( $genre_array, $publisher_array ) {
	
	/*
	 * For the sake of this tutorial, we'll assume
	 * $genre_array and $publisher_array are valid arrays.
	 */
  
	$wp_query_args = array(
		'post_type' => 'book',
		'tax_query' => array(
			'relation' => 'OR',
			array(
				'taxonomy' => 'genre',
				'field'    => 'slug',
				'terms'    => $genre_array,
			),
			array(
				'taxonomy' => 'publisher',
				'field'    => 'slug',
				'terms'    => $publisher_array,
			),
		),
	);
	
	// Generate the transient name.
	$transient_name = 'jr3_' . md5( maybe_serialize( $wp_query_args ) );
	
	$books = get_transient( $transient_name );
	
	if ( ( false === $books ) || ( ! is_array( $books ) ) ) {
		$books = array();
		
		// Run the Query.
		$query = new WP_Query( $wp_query_args );
		if ( is_array( $query->posts ) ) {

			// Rename for output.
			$books = $query->posts;

			// Set our transient using our generated name.
			set_transient( $transient_name, $books, HOUR_IN_SECONDS );
		}
	}

	return $books;
}