我正在使用自定义元字段处理自定义帖子类型post type （如post格式）。我能够根据元键值保存和检索帖子。但我面临的问题是，如果已经选择了该字段的选项，如何限制添加新帖子。即，如果已选择该选项，则用户将为禁用该选项ADD NEW POST.

以下是我迄今为止所做的：

function ps_add_meta_box() {

        add_meta_box(
                \'ps_sectionid\', \'Distinctive Person Format\', \'ps_meta_box_callback\', \'distinctiveperson\',\'side\',\'high\'
        ); //you can change the 4th paramter i.e. post to custom post type name, if you want it for something else

}

add_action( \'add_meta_boxes\', \'ps_add_meta_box\' );


function ps_meta_box_callback( $post ) {

        // Add an nonce field so we can check for it later.
        wp_nonce_field( \'ps_meta_box\', \'ps_meta_box_nonce\' );

        /*
         * Use get_post_meta() to retrieve an existing value
         * from the database and use the value for the form.
         */
        $value = get_post_meta( $post->ID, \'ps_sectionid\', true ); //my_key is a meta_key. Change it to whatever you want

        ?>
        <!--<label for="ps_new_field"><?php _e( "Choose value:", \'choose_value\' ); ?></label>
        <br />  -->
        <input type="radio" name="the_name_of_the_radio_buttons" value="value1" <?php checked( $value, \'value1\' ); ?> >TYpe1<br>
        <input type="radio" name="the_name_of_the_radio_buttons" value="value2" <?php checked( $value, \'value2\' ); ?> >Type2<br>
        <input type="radio" name="the_name_of_the_radio_buttons" value="value3" <?php checked( $value, \'value3\' ); ?> >Type3<br>
        <input type="radio" name="the_name_of_the_radio_buttons" value="value4" <?php checked( $value, \'value4\' ); ?> >type4<br>
        <input type="radio" name="the_name_of_the_radio_buttons" value="value5" <?php checked( $value, \'value5\' ); ?> >Type5<br>

        <?php

}

function ps_save_meta_box_data( $post_id ) {

        /*
         * We need to verify this came from our screen and with proper authorization,
         * because the save_post action can be triggered at other times.
         */

        // Check if our nonce is set.
        if ( !isset( $_POST[\'ps_meta_box_nonce\'] ) ) {
                return;
        }

        // Verify that the nonce is valid.
        if ( !wp_verify_nonce( $_POST[\'ps_meta_box_nonce\'], \'ps_meta_box\' ) ) {
                return;
        }

        // If this is an autosave, our form has not been submitted, so we don\'t want to do anything.
        if ( defined( \'DOING_AUTOSAVE\' ) && DOING_AUTOSAVE ) {
                return;
        }

        // Check the user\'s permissions.
        if ( !current_user_can( \'edit_post\', $post_id ) ) {
                return;
        }


        // Sanitize user input.
        $new_meta_value = ( isset( $_POST[\'the_name_of_the_radio_buttons\'] ) ? sanitize_html_class( $_POST[\'the_name_of_the_radio_buttons\'] ) : \'\' );

        // Update the meta field in the database.
        update_post_meta( $post_id, \'ps_sectionid\', $new_meta_value );

}

add_action( \'save_post\', \'ps_save_meta_box_data\' );