วิธีการเพิ่ม "Blog" slug ไว้ข้างหน้า Posts URL

functions.php

<?php 

/**
 * อ่านบทความเพิ่มเติมได้ที่: https://coderblitz.com/blog/add-blog-slug-in-front-posts/
 * 
 * Tip: หลังจากเพิ่มกฎ Rewrite แล้วอย่าลืมไปที่ Settings > Permalinks แล้วกด “Save Changes” เพื่อรีเฟรช Rewrite rules ด้วย
 */

/**
 * Filter the post permalink to add 'blog/' slug in front of post slug.
 */
add_filter( 'post_type_link', static function ( string $post_link, WP_Post $post ): string {
    if ( $post->post_type === 'post' ) {
        return home_url( '/blog/' . $post->post_name . '/' );
    }
    return $post_link;
}, 10, 2 );

add_filter( 'post_link', static function ( string $permalink, WP_Post $post ): string {
    if ( $post->post_type === 'post' ) {
        return home_url( '/blog/' . $post->post_name . '/' );
    }
    return $permalink;
}, 10, 2 );

/**
 * Add custom rewrite rules for 'blog/' slug before post slug.
 */
add_action( 'init', static function (): void {
    add_rewrite_rule( '^blog/([^/]+)/?$', 'index.php?name=$matches[1]', 'top' );
} );

/**
 * Redirect posts to always include 'blog/' in the URL.
 */
add_action( 'template_redirect', static function (): void {
    if ( is_singular( 'post' ) ) {
        global $post;

        $current_url = home_url( untrailingslashit( add_query_arg( null, null ) ) );
        $correct_url = untrailingslashit( get_permalink( $post ) );

        if ( $current_url !== $correct_url ) {
            wp_redirect( $correct_url, 301 );
            exit;
        }
    }
} );