Source

File: wp-includes/post.php

function get_page_by_path( $page_path, $output = OBJECT, $post_type = 'page' ) {
	global $wpdb;

	$last_changed = wp_cache_get_last_changed( 'posts' );

	$hash      = md5( $page_path . serialize( $post_type ) );
	$cache_key = "get_page_by_path:$hash:$last_changed";
	$cached    = wp_cache_get( $cache_key, 'posts' );
	if ( false !== $cached ) {
		// Special case: '0' is a bad `$page_path`.
		if ( '0' === $cached || 0 === $cached ) {
			return;
		} else {
			return get_post( $cached, $output );
		}
	}

	$page_path     = rawurlencode( urldecode( $page_path ) );
	$page_path     = str_replace( '%2F', '/', $page_path );
	$page_path     = str_replace( '%20', ' ', $page_path );
	$parts         = explode( '/', trim( $page_path, '/' ) );
	$parts         = array_map( 'sanitize_title_for_query', $parts );
	$escaped_parts = esc_sql( $parts );

	$in_string = "'" . implode( "','", $escaped_parts ) . "'";

	if ( is_array( $post_type ) ) {
		$post_types = $post_type;
	} else {
		$post_types = array( $post_type, 'attachment' );
	}

	$post_types          = esc_sql( $post_types );
	$post_type_in_string = "'" . implode( "','", $post_types ) . "'";
	$sql                 = "
		SELECT ID, post_name, post_parent, post_type
		FROM $wpdb->posts
		WHERE post_name IN ($in_string)
		AND post_type IN ($post_type_in_string)
	";

	$pages = $wpdb->get_results( $sql, OBJECT_K );

	$revparts = array_reverse( $parts );

	$foundid = 0;
	foreach ( (array) $pages as $page ) {
		if ( $page->post_name == $revparts[0] ) {
			$count = 0;
			$p     = $page;

			/*
			 * Loop through the given path parts from right to left,
			 * ensuring each matches the post ancestry.
			 */
			while ( 0 != $p->post_parent && isset( $pages[ $p->post_parent ] ) ) {
				$count++;
				$parent = $pages[ $p->post_parent ];
				if ( ! isset( $revparts[ $count ] ) || $parent->post_name != $revparts[ $count ] ) {
					break;
				}
				$p = $parent;
			}

			if ( 0 == $p->post_parent && count( $revparts ) == $count + 1 && $p->post_name == $revparts[ $count ] ) {
				$foundid = $page->ID;
				if ( $page->post_type == $post_type ) {
					break;
				}
			}
		}
	}

	// We cache misses as well as hits.
	wp_cache_set( $cache_key, $foundid, 'posts' );

	if ( $foundid ) {
		return get_post( $foundid, $output );
	}
}