Related posts based on other field

Hi,

Thanks for your answer.
When you say “use the appropriate fields for Yoast”, it’s on this line ?
AND ( $wpdb->postmeta.meta_key = '_visibility' AND $wpdb->postmeta.meta_value = 'visible' )

I have to change _visibility by _yoast_wpseo_focuskw but what i have to set instead of “visible” for meta_value ?

I have for each post ID a _yoast_wpseo_focuskw meta_key but i can have the same meta_value for several post ID.
I want to display on a post, all posts (in a specific category) with the same meta_value.

Value must be same values that the actually post.

Example : on my post, i’ve got the yoast_wpseo_focuskw which is “toto”. I want as related posts all post ID in category “book” where yoast_wpseo_focuskw is “toto”.

Ok.
I know what i want to do but not how to do.

Here AND ( $wpdb->postmeta.meta_key = '_yoast_wpseo_focuskw' AND $wpdb->postmeta.meta_value = 'visible' ) i have just to change “= visible” by = the post.ID postmeta.meta_value.
Just don’t know how to write it.

I tried but i’ve got php error messages.
So, i’m going to try another thing.

Is it possible to find related posts where post_title are exactly the same as the post display ?

Example : I open a post in my browser where post_title is “Best wordpress theme” and i want to display only related posts with exactly the same post_title “Best wordpress theme”.

I set 0 in the “Limit content to be compared” field, but it doesn’t work.
Maybe a change in php file ?

As you can see in this page, post title is “Quand les gens tombent”.

Related posts are display in the sidebar under “LES CHRONIQUES”.
And these posts aren’t in relation with post.
http://www.livresque-du-noir.fr/quand-les-anges-tombent/

No. I had delete the extra piece of code.

In my example, post-title “Quand les anges tombent” can be translate as “When angels fall”.
And related posts found by the plugin are “I hear the noise of the wings which fall” and “Torn off wings of the angels”

Here is a php code that a guy made which can only display related posts with same post title.
It just display related posts but without links, thumbnails, author…
Maybe it’s possible to use a part of this code with yours ?

<?php
/*
Plugin Name: WPSE Get Duplicate Post Titles
Plugin URI:  http://wordpress.stackexchange.com/q/220279/31545
Description: Displays posts with the same title in the sidear
Version:     1.0.0
Author:      Pieter Goosen
Author URI:  http://wordpress.stackexchange.com/users/31545/pieter-goosen
License:     GPL2
License URI: https://www.gnu.org/licenses/gpl-2.0.html
*/

add_filter( 'posts_where', function ( $where, $q ) use ( &$wpdb )
{
    // Get the value from our new wpse_title_match query var
    $title_match = $q->get( 'wpse_title_match' );

    // Make sure we have a value, if not, bail
    if ( !$title_match )
        return $where;

    /**
     * Lets alter the SQL WHERE clause
     *
     * Note, this will be an exact 1 to 1 match, adjust as necessary
     */
    $where .= $wpdb->prepare(
        " AND {$wpdb->posts}.post_title = %s ",
        $title_match
    );

    return $where;
}, 10, 2 );

class WPSE_Get_Duplicate_Post_titles extends WP_Widget
{

    public function __construct()
    {
        parent::__construct(
            'widget_get_duplicate_post_titles',
            _x( 'Post Title duplicates', 'Post Title duplicates' ),
            [ 'description' => __( 'Displays posts which share the same post title.' ) ]
        );
        $this->alt_option_name = 'widget_get_duplicate_post_titles';

        add_action( 'save_post',    [$this, 'flush_widget_cache'] );
        add_action( 'deleted_post', [$this, 'flush_widget_cache'] );
        add_action( 'switch_theme', [$this, 'flush_widget_cache'] );
    }

    public function widget( $args, $instance )
    {
        $cache = [];
        if ( ! $this->is_preview() ) {
            $cache = wp_cache_get( 'widget_bpfi', 'widget' );
        }

        if ( ! is_array( $cache ) ) {
            $cache = [];
        }

        if ( ! isset( $args['widget_id'] ) ) {
            $args['widget_id'] = $this->id;
        }

        if ( isset( $cache[ $args['widget_id'] ] ) ) {
            echo $cache[ $args['widget_id'] ];
            return;
        }

        ob_start();

        $title          = ( ! empty( $instance['title'] ) ) ? $instance['title'] : __( 'Post Title Duplicates' );
        /** This filter is documented in wp-includes/default-widgets.php */
        $title          = apply_filters( 'widget_title', $title, $instance, $this->id_base );

        // ADD YOUR CUSTOM PHP CODE HERE FOR EXECUTION TO DISPLAY ON FRONT END
        // First make sure this a single post page
        if ( is_single() ) { // We are on a single page
            // Get the current post object
            $post_object = $GLOBALS['wp_the_query']->get_queried_object();

            // Run our query to get the posts with duplicate titles
            $args = [
                'posts_per_page'   => -1, // Get all posts
                'post_type'        => 'post',
                'wpse_title_match' => $post_object->post_title,
                'post__not_in'     => [$post_object->ID], // Exclude current post
                'tax_query'        => [
                    [
                        'taxonomy' => 'category',
                        'field'    => 'slug',
                        'terms'    => 'chroniques'
                    ]
                ],
                // Any other arguments
            ];
            $loop = new WP_Query( $args );

            // Run the loop
            if ( $loop->have_posts() ) {
                while ( $loop->have_posts() ) {
                    $loop->the_post();

                    // Display your posts
                    the_title() . "\n";

                }
                wp_reset_postdata();
            }
        }

        echo $args['after_widget']; 

        if ( ! $this->is_preview() ) {
            $cache[ $args['widget_id'] ] = ob_get_flush();
            wp_cache_set( 'widget_bpfi', $cache, 'widget' );
        } else {
            ob_end_flush();
        }
    }

    public function update( $new_instance, $old_instance )
    {
        $instance                   = $old_instance;
        $instance['title']          = strip_tags( $new_instance['title'] );
        $this->flush_widget_cache();

        $alloptions = wp_cache_get( 'alloptions', 'options' );
        if ( isset($alloptions['widget_get_duplicate_post_titles']) )
            delete_option('widget_get_duplicate_post_titles');

        return $instance;
    }

    public function flush_widget_cache()
    {
        wp_cache_delete('widget_bpfi', 'widget');
    }

    public function form( $instance )
    {

        $title      = isset( $instance['title'] ) ? esc_attr( $instance['title'] ) : '';
        ?>

        <p>
            <label for="<?php echo $this->get_field_id( 'title' ); ?>"><?php _e( 'Title:' ); ?></label>
            <input class="widefat" id="<?php echo $this->get_field_id( 'title' ); ?>" name="<?php echo $this->get_field_name( 'title' ); ?>" type="text" value="<?php echo $title; ?>" />
        </p>

    <?php
    }

}

add_action( 'widgets_init', function ()
{
    register_widget( 'WPSE_Get_Duplicate_Post_titles' );
});

add_filter( 'sidebars_widgets', function ( $sidebars_widgets )
{
    // Return our filter when we are on admin screen
    if ( is_admin() )
        return $sidebars_widgets;

    // Make sure we are not on the blog page, if we are, bail
    if ( is_single() )
        return $sidebars_widgets;

    /**
     * Widget we need to target. This should be the name/id we used to register it
     *
     * EXAMPLE
     *   parent::__construct(
            'widget_get_duplicate_post_titles',
            _x( 'Blog Page Featured Image', 'Blog page featured image' ),
            [ 'description' => __( 'Displays the featured image for the pge set as blog page.' ) ]
        );
     *
     */
    $custom_widget  = 'widget_get_duplicate_post_titles';

    // See if our custom widget exists is any sidebar, if so, get the array index
    foreach ( $sidebars_widgets as $sidebars_key=>$sidebars_widget ) {
        // Skip the wp_inactive_widgets set, we do not need them
        if ( $sidebars_key == 'wp_inactive_widgets' )
        continue;

        // Only continue our operation if $sidebars_widget are not an empty array
        if ( $sidebars_widget ) {
            foreach ( $sidebars_widget as $k=>$v ) {

                /**
                 * Look for our custom widget, if found, unset it from the $sidebars_widgets array
                 * @see stripos()
                 */
                if ( stripos( $v, $custom_widget ) !== false )
                    unset( $sidebars_widgets[$sidebars_key][$k] );
            } // endforeach $sidebars_widget
        } // endif $sidebars_widget
    } // endforeach $sidebars_widgets

    return $sidebars_widgets;
});