WordPress : Retrieve a post ID given its path.

wp-get_id_by_path.php

<?php

if ( ! function_exists('get_ID_by_path') ) :

	/**
	 * Retrieves an ID given its path.
	 *
	 * @global $wpdb
	 *
	 * @param  string  $page_path  Page path
	 * @param  string  $post_type  Optional. Post type. Default page.
	 * @return mixed   Null when complete.
	 */

	function get_ID_by_path ( $page_path, $post_type = 'page' )
	{
		$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( 'esc_sql', $parts );
		$parts = array_map( 'sanitize_title_for_query', $parts );

		$in_cache = implode( ',', $parts );
		$cached_id = wp_cache_get( 'get_id_by_path_' . $in_cache, 'skl-posts' );

		if ( $cached_id ) {
			return $cached_id;
		}

		$q = get_queried_object();

		if ( isset( $q->post_name ) && $q->post_name == end( $parts ) ) {
			$found_id = $q->ID;
		}
		else {
			global $wpdb;

			reset( $parts );

			$in_string = "'". implode( "','", $parts ) . "'";
			$post_type_sql = $post_type;
			$wpdb->escape_by_ref( $post_type_sql );
			$sql = "
				SELECT ID, post_name, post_parent
				FROM $wpdb->posts
				WHERE post_name IN ($in_string)
				AND (post_type = '$post_type_sql'
				OR post_type = 'attachment')
			";

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

			$revparts = array_reverse( $parts );

			$found_id = 0;
			foreach ( (array) $pages as $page ) {
				if ( $page->post_name == $revparts[0] ) {
					$count = 0;
					$p = $page;
					while ( $p->post_parent != 0 && isset( $pages[ $p->post_parent ] ) ) {
						$count++;
						$parent = $pages[ $p->post_parent ];
						if ( ! isset( $revparts[ $count ] ) || $parent->post_name != $revparts[ $count ] )
							break;
						$p = $parent;
					}

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

		wp_cache_set( 'get_id_by_path_' . $in_cache, $found_id, 'skl-posts' );
		return $found_id;
	}

endif;