Ecco la terza parte del tutorial su come sviluppare un template di WordPress, spiega custom queries, il WP_Query, il get_posts e il query_posts.
Per accedere alle altre parti del tutorial vedi il post Tutorial di WordPress Template.
Custom Queries
Puoi customizzare i post risultanti dal “loop” usando custom post queries, come WP_Query, get_posts o query_posts.
- WP_Query è di generale utilità, è un po più complessa, con meno restrizioni, si può utilizzare ovunque
- get_postssi può utilizzare ovunque
- query_posts deve essere usato solo se devi modificare la query principale della pagina
Se devi accedere al loop originale della pagina dopo una custom query, puoi usare questo codice:
$tmp_post = $post; // My custom query here $post = $tmp_post;
Il WP_Query
La query raccomandata da usare nei template di WordPress è WP_Query. Puoi usare WP_Query con la forma semplificata come qua:
$the_query = new WP_Query('post_type=post&cat=6&order=asc&orderby=id'); while ($the_query->have_posts()) : $the_query->the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile;
Aggiungi parametri addizionali come quelli quà sotto (come page_id, tag, tag_id, etc..) a seconda delle necessità.
Oppure puoi costruire la query con un array di dati con un codice come questo, qui sono presenti tutte le possibilità di query:
$args = array( 'post_type' => 'post', // 'post', 'page', 'any', custom type 'post_status' => 'publish', // 'publish, 'pending', 'draft', 'future', 'private', 'trash' 'numberposts' => 5, // Limit the query to a numberposts 'offset' => 1, // Query start from result offset 'order' => 'asc', // 'asc', 'desc' 'orderby' => 'id', // 'none', 'id', 'author', 'title', 'date', 'modified', 'parent', 'rand', 'comment_count', 'menu_order', 'meta_value', 'meta_value_num' 'meta_key' => 'keyname' // If you are using orderby 'meta_value' or 'meta_value_num' 'year' => '2001', // Query by time. 4 digit year 'monthnum' => '6', // Query by time. Month number (from 1 to 12) 'w' => '0', // Query by time. Week of the year (from 0 to 53) 'day' => '1', // Query by time. Day of the month (from 1 to 31) 'hour' => '11', // Query by time. Hour (from 0 to 23) 'minute' => '12', // Query by time. Minute (from 0 to 60) 'second' => '19', // Query by time. Second (from 0 to 60) 'p' => '10', // Query by post ID 'name' => 'myname', // Query by post slug 'page_id' => '10', // Query by page ID 'pagename' => 'myname', // Query by page slug 'post_parent' => '10', // Query by post ID. Return just the child Pages 'post__in' => '', // Query by post ID. Specify posts to retrieve 'post__not_in' => '', // Query by post ID. Specify post NOT to retrieve 'post__in' => array( '595', '33', 44 ), 'author' => '123', // Query by author ID 'author' => array( '-12','-34','-56' ), // Filter out author ID 'author_name' => 'rami', // Query by author name 'showposts' => '5', // Limits the query to 5 results 'cat' => '4', // Query by category ID 'cat' => array( '-12','-34','-56' ), // Filter out category ID 'category_name' => 'staff', // Query by category slug 'category__and' => array( '2','6' ), // Query by category ID. Filter posts that are in both categories 2 and 6 'category__in' => array( '2','6' ), // Query by category ID. Filter posts that are either in category 2 OR 6 'category__not_in' => array( '2','6' ), // Query by category ID. Filter posts that are not either in category 2 OR 6 'tag' => 'cooking', // Query by tag slug 'tag' => 'bread+baking+recipe', // Query by tag slug. That have "all" of these tags 'tag' => array( 'bread','baking' ), // Query by tag slug. That have "either" of these tags 'tag_id' => '13', // Query by tag ID 'tag__and' => array( '37','47' ), // Query by tag ID. Tagged with both tag id 37 and tag id 47 'tag__in' => array( '37','47' ), // Query by tag ID. Tagged with either tag id 37 or tag id 47 'tag__not_in' => array( '37','47' ), // Query by tag ID. Tagged with neither tag id 37 and tag id 47 'tag_slug__and' => array( 'bread','baking' ), // Query by tag slug. Tagged with both bread and baking 'tag_slug__in' => array( 'bread','baking' ), // Query by tag slug. Tagged with either bread or baking 'meta_query' => array( // You can query by custom fields array( 'key' => 'color', 'value' => 'blue', 'compare' => 'NOT LIKE' ), array( // You can query multiple custom fields 'key' => 'price', 'value' => array( 20, 100 ), 'type' => 'numeric', // Custom field type. 'NUMERIC', 'BINARY', 'CHAR', 'DATE', 'DATETIME', 'DECIMAL', 'SIGNED', 'TIME', 'UNSIGNED' 'compare' => 'BETWEEN' // Operator to test. 'LIKE', 'NOT LIKE', 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN', >, >= <, <= ) ), 'tax_query' => array( // You can query by taxonimies 'relation' => 'AND', // Display posts that are in categories with id 103, 115, 206 AND not tagged with 'bruce', under 'people' custom taxonomy array( 'taxonomy' => 'category', // 'tag', 'category', 'custom taxonomy' 'field' => 'id', 'terms' => array( 103, 115, 206 ), ), array( 'taxonomy' => 'people', 'field' => 'slug', // 'id' or 'slug' 'terms' => array( 'bruce' ), 'operator' => 'NOT IN', // Operator to test. 'LIKE', 'NOT LIKE', 'IN', 'NOT IN', 'BETWEEN', 'NOT BETWEEN', >, >= <, <= ) ) ); $the_query = new WP_Query( $args ); while ($the_query->have_posts()) : $the_query->the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile;
Le query qua sopra non possono filtrare i post da un margine di tempo fino al presente, quindi le query come “Post negli ultimi 30 giorni” o “Post dall’anno precedente” non sono possibili con la query di base, e richiedono l’uso del filtro posts_where, come:
// Return posts from the last 30 days: function filter_where( $where = '' ) { $where .= " AND post_date > '" . date('Y-m-d', strtotime('-30 days')) . "'"; return $where; } add_filter( 'posts_where', 'filter_where' ); $query = new WP_Query( $query_string ); while ($the_query->have_posts()) : $the_query->the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile; // Return posts 30 to 60 days old function filter_where( $where = '' ) { $where .= " AND post_date >= '" . date('Y-m-d', strtotime('-60 days')) . "'" . " AND post_date <= '" . date('Y-m-d', strtotime('-30 days')) . "'"; return $where; } add_filter( 'posts_where', 'filter_where' ); $query = new WP_Query( $query_string ); while ($the_query->have_posts()) : $the_query->the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile;
Successivamente quando hai settato la query puoi usare i risultati in questo modo, usando le variabili di post dentro ‘il loop’:
while ($the_query->have_posts()) : $the_query->the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile;
Per vedere tutte le funzioni e le variabili a cui puoi accedere all’interno del “loop” vedi Contenuti WordPress Template.
L’oggetto Wp_query contiene anche alcuni utili parametri di query:
$wp_query->query; // Holds the query string that was passed to the $wp_query object $wp_query->query_vars; // An associative array containing the dissected $query $wp_query->queried_object; // Holds information on the requested category, author, post or page $wp_query->queried_object_id; // Holds the ID of the requested category, author, post or page $wp_query->posts; // Gets filled with the requested posts from the database $wp_query->post_count; // The number of posts being displayed $wp_query->current_post; // Index of the post currently being displayed $wp_query->post; // The post currently being displayed $wp_query->is_single // Booleans dictating what type of request this is. Can be also is_page, is_archive, is_preview, is_date, is_year, is_month, is_time, is_author, is_category, is_tag, is_tax, is_search, is_feed, is_comment_feed, is_trackback, is_home, is_404, is_comments_popup, is_admin, is_attachment, is_singular, is_robots, is_posts_page, is_paged
Il get_posts
Questo è il secondo metodo per customizzate la query del “loop”. Puoi usare la funzione get_posts così:
$args = array( 'category' => , // Query by category ID 'order' => 'DESC', // 'asc', 'desc' 'orderby' => 'post_date', // 'none', 'id', 'author', 'title', 'date', 'modified', 'parent', 'rand', 'comment_count', 'menu_order', 'meta_value', 'meta_value_num' 'include' => , 'exclude' => , 'numberposts' => 5, // Limit the query to a numberposts 'offset' => 0, // Query start from result offset 'meta_key' => , // If you are using orderby 'meta_value' or 'meta_value_num' 'meta_value' => , // If you are using orderby 'meta_value' or 'meta_value_num' 'post_type' => 'post', // 'post', 'page', 'any', custom type 'post_mime_type' => , 'post_parent' => , // Query by post ID. Return just the child Pages 'post_status' => 'publish' // 'publish, 'pending', 'draft', 'future', 'private', 'trash' ); $myposts = get_posts( $args ); foreach( $myposts as $post ) : setup_postdata($post); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endforeach;
Per vedere tutte le funzioni e le variabili a cui puoi accedere all’interno del “loop” vedi Contenuti WordPress Template.
Il query_posts
L’ultimo metodo non può essere usato dovunque, ma solo se si deve modificare la query principale della pagina. Puoi usare la funzione query_posts così:
$args = array( 'p' => '5', // Query by post ID 'category' => , // Query by category ID 'category_name' => 'The Category Name', // Query by category slug 'order' => 'DESC', // 'asc', 'desc' 'orderby' => 'post_date', // 'none', 'id', 'author', 'title', 'date', 'modified', 'parent', 'rand', 'comment_count', 'menu_order', 'meta_value', 'meta_value_num' 'include' => , 'exclude' => , 'numberposts' => 5, // Limit the query to a numberposts 'offset' => 0, // Query start from result offset 'year' => '2001', // Query by time. 4 digit year 'monthnum' => '6', // Query by time. Month number (from 1 to 12) 'w' => '0', // Query by time. Week of the year (from 0 to 53) 'day' => '1', // Query by time. Day of the month (from 1 to 31) 'hour' => '11', // Query by time. Hour (from 0 to 23) 'minute' => '12', // Query by time. Minute (from 0 to 60) 'second' => '19', // Query by time. Second (0 to 60) 'meta_key' => , // If you are using orderby 'meta_value' or 'meta_value_num' 'meta_value' => , // If you are using orderby 'meta_value' or 'meta_value_num' 'post_type' => 'post', // 'post', 'page', 'any', custom type 'post_mime_type' => , 'post_parent' => , // Query by post ID. Return just the child Pages 'post_status' => 'publish' // 'publish, 'pending', 'draft', 'future', 'private', 'trash' ); query_posts( $args ); while ( have_posts() ) : the_post(); // Inside The Loop is here // Use functions like the_title(); or access object variables like $post->post_title; endwhile; wp_reset_query();
Per vedere tutte le funzioni e le variabili a cui puoi accedere all’interno del “loop” vedi Contenuti WordPress Template.
Il Tutorial
Fine della seconda parte del Tutorial di WordPress Template.
La prossima parte del tutorial coprirà funzioni utili e plugin utili.
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