Remove prefix from CPT URL

arunas-no-prefix-cpt.php

<?php

/*
* Plugin Name: Arunas' No Prefix for CPT
* Version: 1.0.0
* Description: Remove prefix from CPT URL
* Plugin URI: https://gist.github.com/ideag/60d4b1e6185e62fa9a903bcf600f8a95
* Author: Arūnas Liuiza
* Author URI: https://www.arunas.co/
*/

add_action( 'plugins_loaded', array( 'Arunas_No_Prefix_CPT_Class', 'get_instance' ) );

class Arunas_No_Prefix_CPT_Class {
	protected $options = array(
		'post_type' => 'arunas_cpt',
	);
  private static $instance;
  public static function get_instance() {
    if (null === self::$instance) {
      self::$instance = new self();
    }
    return self::$instance;
  }
  public function __construct() {
		add_filter( 'post_type_link', array( $this, 'cpt_remove_base' ), 10, 2 );
		add_action( 'pre_get_posts', array( $this, 'cpt_fix_query' ), 101, 1 );
		add_filter( 'url_to_postid', array( $this, 'cpt_fix_url_to_postid' ), 100, 1 );
		// Prevent slug clashes.
		add_filter( 'wp_unique_post_slug', array( $this, 'cpt_slug' ), 10, 6 );  
  }
	public function cpt_remove_base( $post_link, $post ) {
		if ( $this->options['post_type'] !== $post->post_type ) {
			return $post_link;
		}
		if ( 'publish' !== $post->post_status ) {
			return $post_link;
		}
		$post_link = str_replace( "/{$post->post_type}/", '/', $post_link );
		return $post_link;
	}
	public function cpt_fix_query( $query ) {
		global $wp;
		if ( is_admin() ) {
			return;
		}

		if ( ! $query->is_main_query() ) {
			return;
		}
		if ( $query->get( 'queried_object_id' ) ) {
			return;
		}
		if ( ! $query->get( 'pagename' ) && ! $query->get( 'attachment' ) && ! $query->get( 'name' ) && ! $query->get( 'category_name' ) && ! $query->is_404() ) {
			return;
		}

		$post_name = $query->get( 'pagename' );
		$post_name = ( ! $post_name ) ? $this->_build_page_name( $query->get( 'attachment' ) ) : $post_name;
		$post_name = ( ! $post_name ) ? $query->get( 'name' ) : $post_name;
		$post_name = ( ! $post_name ) ? $query->get( 'category_name' ) : $post_name;
		$post_name = ( ! $post_name ) ? $wp->request : $post_name;

		if ( ! $post_name ) {
			return;
		}

		$post_slug = $post_name;
		$post_slug = substr( $post_slug, -1 ) == '/' ? substr( $post_slug, 0, -1 ) : $post_slug;
		$pos       = strrpos( $post_slug, '/' );
		$post_slug = substr( $post_slug, false !== $pos ? $pos + 1 : 0 );
		$post      = get_page_by_path( $post_name, OBJECT, $this->options['post_type'] );

		if ( ! $post ) {
			return false;
		}

		$post_type   = $post->post_type;
		$post_parent = (int) $post->post_parent;

		$query->tax_query     = null;
		$query->is_attachment = false;
		$query->is_category   = false;
		$query->is_archive    = false;
		$query->is_page       = false;
		$query->is_404        = false;
		$query->is_single     = true;
		$query->is_singular   = true;
		$query->set( 'page', '' );
		$query->query['page'] = '';
		$query->set( 'pagename', null );
		unset( $query->query['pagename'] );
		$query->set( 'attachment', null );
		unset( $query->query['attachment'] );
		$query->set( 'category_name', null );
		unset( $query->query['category_name'] );
		$query->set( 'post_type', $post_type );
		$query->query['post_type'] = $post_type;
		$query->set( 'name', $post_name );
		$query->query['name'] = $post_name;
		$query->set( $post_type, $post_name );
		$query->query[ $post_type ] = $post_name;
	}
	public function cpt_fix_url_to_postid( $url ) {
		// if we get a result the standard way, do nothing.
		remove_filter( 'url_to_postid', array( $this, 'cpt_fix_url_to_postid' ), 100, 1 );
		$id = url_to_postid( $url );
		add_filter( 'url_to_postid', array( $this, 'cpt_fix_url_to_postid' ), 100, 1 );
		if ( 0 !== $id ) {
			return $url;
		}

		// Try for flexi page. If works, convert url to one with ?p=ID.
		$home = home_url();
		$path = untrailingslashit( str_replace( $home, '', $url ) );
		$path = explode( '/', $path );
		$name = array_pop( $path );
		$post_obj = get_page_by_path( $name, OBJECT, 'flexi_page' );
		if ( $post_obj ) {
			$url = add_query_arg( 'p', $post_obj->ID, $home );
		}

		return $url;
	}
	public function cpt_slug( $slug, $post_ID, $post_status, $post_type, $post_parent, $original_slug ) {
		global $wpdb;
		$post_types_no_conflict = array( 'post', 'page', 'attachment', $this->options['post_type'] );

		// should we do cross post-type checking?
		if ( ! in_array( $post_type, $post_types_no_conflict ) ) {
			return $slug;
		}

		$post_types_in = implode( "', '", $post_types_no_conflict );
		$post_types_in = "'{$post_types_in}'";
		$slug_base     = preg_replace( '/(\-[0-9]+)$/ims', '', $slug );
		$slug_regex    = "^{$slug_base}(\-[0-9]+)?$";
		$similar_slugs = $wpdb->get_col(
			$wpdb->prepare(
				"SELECT post_name FROM {$wpdb->posts} WHERE post_name RLIKE %s AND post_type IN ( $post_types_in ) AND ID != %d AND post_status = 'publish'",
				$slug_regex,
				$post_ID
			)
		);

		// do we have any similar slugs?
		if ( ! $similar_slugs ) {
			return $slug;
		}
		// is the original slug in the list?
		if ( ! in_array( $slug, $similar_slugs ) ) {
			return $slug;
		}

		// find the largest slug number.
		$max = 1;
		foreach ( $similar_slugs as $similar_slug ) {
			$similar_slug = explode( '-', $similar_slug );
			$no           = (int) end( $similar_slug );

			$max = $no > $max ? $no : $max;
		}

		++$max;
		$new_slug = "{$slug_base}-{$max}";

		return $new_slug;
	}
  
	private function _build_page_name( $post_slug ) {
		global $wpdb;

		if ( ! $post_slug ) {
			return $post_slug;
		}

		$post_id = $wpdb->get_var(
			$wpdb->prepare(
				"SELECT `ID` FROM {$wpdb->posts} WHERE post_name = %s",
				$post_slug
			)
		);

		$permalink = get_permalink( $post_id );
		$name      = str_replace( home_url(), '', $permalink );

		return $name;
	}

}