webmention.php

function webmention_url_to_postid( $url ) {
	$id = wp_cache_get( base64_encode( $url ), 'webmention_url_to_postid' );

	if ( $id ) {
		return apply_filters( 'webmention_post_id', $id, $url );
	}

	if ( '/' === wp_make_link_relative( trailingslashit( $url ) ) ) {
		return apply_filters( 'webmention_post_id', get_option( 'webmention_home_mentions' ), $url );
	}

	$id = url_to_postid( $url );

	if ( ! $id && post_type_supports( 'attachment', 'webmentions' ) ) {
		$ext = pathinfo( wp_parse_url( $url, PHP_URL_PATH ), PATHINFO_EXTENSION );

		if ( ! empty( $ext ) ) {
			$id = attachment_url_to_postid( $url );
		}
	}

	wp_cache_set( base64_encode( $url ), $id, 'webmention_url_to_postid', 300 );

	return apply_filters( 'webmention_post_id', $id, $url );
}