Prefer Pages over CPT

prefer-pages-over-cpt.php

/* Prefer Pages over CPT */

function sg_page_before_cpt( $query ) {

	$cpt_slug = 'my_cpt_slug';
	$cpt_rewrite_slug = 'my_cpt_rewrite_slug';

	if( isset( $query->query_vars[$cpt_slug] ) && $slug = $query->query_vars[$cpt_slug] ) {
		$slug = "$cpt_rewrite_slug/$slug";
		if( get_page_by_path( $slug ) ) {
			$query->query_vars['pagename'] = $slug;
			unset( $query->query_vars[$cpt_slug] );
			unset( $query->query_vars['post_type'] );
			unset( $query->query_vars['name'] );
		}
	}

	return $query;
}
if( ! is_admin() ) add_action( 'parse_request', 'sg_page_before_cpt' );


/* Alternative using `request` filter */

function sg_page_before_cpt2( $query_vars ) {
	if ( isset( $query_vars['umc_article'] ) && $slug = $query_vars['umc_article'] ) {
		$slug = hcps_umc_options( 'umc_article_slug' ) . "/$slug";
		if ( get_page_by_path( $slug ) ) {
			$query_vars['pagename'] = $slug;
			unset( $query_vars['umc_article'] );
			unset( $query_vars['post_type'] );
			unset( $query_vars['name'] );
		}
	}
	return $query_vars;
}
if ( ! is_admin() ) add_filter( 'request', 'sg_page_before_cpt2' );