Source

File: wp-includes/class-wp-query.php

public function parse_query( $query = '' ) {
		if ( ! empty( $query ) ) {
			$this->init();
			$this->query      = wp_parse_args( $query );
			$this->query_vars = $this->query;
		} elseif ( ! isset( $this->query ) ) {
			$this->query = $this->query_vars;
		}

		$this->query_vars         = $this->fill_query_vars( $this->query_vars );
		$qv                       = &$this->query_vars;
		$this->query_vars_changed = true;

		if ( ! empty( $qv['robots'] ) ) {
			$this->is_robots = true;
		} elseif ( ! empty( $qv['favicon'] ) ) {
			$this->is_favicon = true;
		}

		if ( ! is_scalar( $qv['p'] ) || $qv['p'] < 0 ) {
			$qv['p']     = 0;
			$qv['error'] = '404';
		} else {
			$qv['p'] = intval( $qv['p'] );
		}

		$qv['page_id']  = absint( $qv['page_id'] );
		$qv['year']     = absint( $qv['year'] );
		$qv['monthnum'] = absint( $qv['monthnum'] );
		$qv['day']      = absint( $qv['day'] );
		$qv['w']        = absint( $qv['w'] );
		$qv['m']        = is_scalar( $qv['m'] ) ? preg_replace( '|[^0-9]|', '', $qv['m'] ) : '';
		$qv['paged']    = absint( $qv['paged'] );
		$qv['cat']      = preg_replace( '|[^0-9,-]|', '', $qv['cat'] );    // Comma-separated list of positive or negative integers.
		$qv['author']   = preg_replace( '|[^0-9,-]|', '', $qv['author'] ); // Comma-separated list of positive or negative integers.
		$qv['pagename'] = trim( $qv['pagename'] );
		$qv['name']     = trim( $qv['name'] );
		$qv['title']    = trim( $qv['title'] );
		if ( '' !== $qv['hour'] ) {
			$qv['hour'] = absint( $qv['hour'] );
		}
		if ( '' !== $qv['minute'] ) {
			$qv['minute'] = absint( $qv['minute'] );
		}
		if ( '' !== $qv['second'] ) {
			$qv['second'] = absint( $qv['second'] );
		}
		if ( '' !== $qv['menu_order'] ) {
			$qv['menu_order'] = absint( $qv['menu_order'] );
		}

		// Fairly insane upper bound for search string lengths.
		if ( ! is_scalar( $qv['s'] ) || ( ! empty( $qv['s'] ) && strlen( $qv['s'] ) > 1600 ) ) {
			$qv['s'] = '';
		}

		// Compat. Map subpost to attachment.
		if ( '' != $qv['subpost'] ) {
			$qv['attachment'] = $qv['subpost'];
		}
		if ( '' != $qv['subpost_id'] ) {
			$qv['attachment_id'] = $qv['subpost_id'];
		}

		$qv['attachment_id'] = absint( $qv['attachment_id'] );

		if ( ( '' !== $qv['attachment'] ) || ! empty( $qv['attachment_id'] ) ) {
			$this->is_single     = true;
			$this->is_attachment = true;
		} elseif ( '' !== $qv['name'] ) {
			$this->is_single = true;
		} elseif ( $qv['p'] ) {
			$this->is_single = true;
		} elseif ( '' !== $qv['pagename'] || ! empty( $qv['page_id'] ) ) {
			$this->is_page   = true;
			$this->is_single = false;
		} else {
			// Look for archive queries. Dates, categories, authors, search, post type archives.

			if ( isset( $this->query['s'] ) ) {
				$this->is_search = true;
			}

			if ( '' !== $qv['second'] ) {
				$this->is_time = true;
				$this->is_date = true;
			}

			if ( '' !== $qv['minute'] ) {
				$this->is_time = true;
				$this->is_date = true;
			}

			if ( '' !== $qv['hour'] ) {
				$this->is_time = true;
				$this->is_date = true;
			}

			if ( $qv['day'] ) {
				if ( ! $this->is_date ) {
					$date = sprintf( '%04d-%02d-%02d', $qv['year'], $qv['monthnum'], $qv['day'] );
					if ( $qv['monthnum'] && $qv['year'] && ! wp_checkdate( $qv['monthnum'], $qv['day'], $qv['year'], $date ) ) {
						$qv['error'] = '404';
					} else {
						$this->is_day  = true;
						$this->is_date = true;
					}
				}
			}

			if ( $qv['monthnum'] ) {
				if ( ! $this->is_date ) {
					if ( 12 < $qv['monthnum'] ) {
						$qv['error'] = '404';
					} else {
						$this->is_month = true;
						$this->is_date  = true;
					}
				}
			}

			if ( $qv['year'] ) {
				if ( ! $this->is_date ) {
					$this->is_year = true;
					$this->is_date = true;
				}
			}

			if ( $qv['m'] ) {
				$this->is_date = true;
				if ( strlen( $qv['m'] ) > 9 ) {
					$this->is_time = true;
				} elseif ( strlen( $qv['m'] ) > 7 ) {
					$this->is_day = true;
				} elseif ( strlen( $qv['m'] ) > 5 ) {
					$this->is_month = true;
				} else {
					$this->is_year = true;
				}
			}

			if ( $qv['w'] ) {
				$this->is_date = true;
			}

			$this->query_vars_hash = false;
			$this->parse_tax_query( $qv );

			foreach ( $this->tax_query->queries as $tax_query ) {
				if ( ! is_array( $tax_query ) ) {
					continue;
				}

				if ( isset( $tax_query['operator'] ) && 'NOT IN' !== $tax_query['operator'] ) {
					switch ( $tax_query['taxonomy'] ) {
						case 'category':
							$this->is_category = true;
							break;
						case 'post_tag':
							$this->is_tag = true;
							break;
						default:
							$this->is_tax = true;
					}
				}
			}
			unset( $tax_query );

			if ( empty( $qv['author'] ) || ( '0' == $qv['author'] ) ) {
				$this->is_author = false;
			} else {
				$this->is_author = true;
			}

			if ( '' !== $qv['author_name'] ) {
				$this->is_author = true;
			}

			if ( ! empty( $qv['post_type'] ) && ! is_array( $qv['post_type'] ) ) {
				$post_type_obj = get_post_type_object( $qv['post_type'] );
				if ( ! empty( $post_type_obj->has_archive ) ) {
					$this->is_post_type_archive = true;
				}
			}

			if ( $this->is_post_type_archive || $this->is_date || $this->is_author || $this->is_category || $this->is_tag || $this->is_tax ) {
				$this->is_archive = true;
			}
		}

		if ( '' != $qv['feed'] ) {
			$this->is_feed = true;
		}

		if ( '' != $qv['embed'] ) {
			$this->is_embed = true;
		}

		if ( '' != $qv['tb'] ) {
			$this->is_trackback = true;
		}

		if ( '' != $qv['paged'] && ( intval( $qv['paged'] ) > 1 ) ) {
			$this->is_paged = true;
		}

		// If we're previewing inside the write screen.
		if ( '' != $qv['preview'] ) {
			$this->is_preview = true;
		}

		if ( is_admin() ) {
			$this->is_admin = true;
		}

		if ( false !== strpos( $qv['feed'], 'comments-' ) ) {
			$qv['feed']         = str_replace( 'comments-', '', $qv['feed'] );
			$qv['withcomments'] = 1;
		}

		$this->is_singular = $this->is_single || $this->is_page || $this->is_attachment;

		if ( $this->is_feed && ( ! empty( $qv['withcomments'] ) || ( empty( $qv['withoutcomments'] ) && $this->is_singular ) ) ) {
			$this->is_comment_feed = true;
		}

		if ( ! ( $this->is_singular || $this->is_archive || $this->is_search || $this->is_feed
				|| ( defined( 'REST_REQUEST' ) && REST_REQUEST && $this->is_main_query() )
				|| $this->is_trackback || $this->is_404 || $this->is_admin || $this->is_robots || $this->is_favicon ) ) {
			$this->is_home = true;
		}

		// Correct `is_*` for 'page_on_front' and 'page_for_posts'.
		if ( $this->is_home && 'page' === get_option( 'show_on_front' ) && get_option( 'page_on_front' ) ) {
			$_query = wp_parse_args( $this->query );
			// 'pagename' can be set and empty depending on matched rewrite rules. Ignore an empty 'pagename'.
			if ( isset( $_query['pagename'] ) && '' === $_query['pagename'] ) {
				unset( $_query['pagename'] );
			}

			unset( $_query['embed'] );

			if ( empty( $_query ) || ! array_diff( array_keys( $_query ), array( 'preview', 'page', 'paged', 'cpage' ) ) ) {
				$this->is_page = true;
				$this->is_home = false;
				$qv['page_id'] = get_option( 'page_on_front' );
				// Correct <!--nextpage--> for 'page_on_front'.
				if ( ! empty( $qv['paged'] ) ) {
					$qv['page'] = $qv['paged'];
					unset( $qv['paged'] );
				}
			}
		}

		if ( '' !== $qv['pagename'] ) {
			$this->queried_object = get_page_by_path( $qv['pagename'] );

			if ( $this->queried_object && 'attachment' === $this->queried_object->post_type ) {
				if ( preg_match( '/^[^%]*%(?:postname)%/', get_option( 'permalink_structure' ) ) ) {
					// See if we also have a post with the same slug.
					$post = get_page_by_path( $qv['pagename'], OBJECT, 'post' );
					if ( $post ) {
						$this->queried_object = $post;
						$this->is_page        = false;
						$this->is_single      = true;
					}
				}
			}

			if ( ! empty( $this->queried_object ) ) {
				$this->queried_object_id = (int) $this->queried_object->ID;
			} else {
				unset( $this->queried_object );
			}

			if ( 'page' === get_option( 'show_on_front' ) && isset( $this->queried_object_id ) && get_option( 'page_for_posts' ) == $this->queried_object_id ) {
				$this->is_page       = false;
				$this->is_home       = true;
				$this->is_posts_page = true;
			}

			if ( isset( $this->queried_object_id ) && get_option( 'wp_page_for_privacy_policy' ) == $this->queried_object_id ) {
				$this->is_privacy_policy = true;
			}
		}

		if ( $qv['page_id'] ) {
			if ( 'page' === get_option( 'show_on_front' ) && get_option( 'page_for_posts' ) == $qv['page_id'] ) {
				$this->is_page       = false;
				$this->is_home       = true;
				$this->is_posts_page = true;
			}

			if ( get_option( 'wp_page_for_privacy_policy' ) == $qv['page_id'] ) {
				$this->is_privacy_policy = true;
			}
		}

		if ( ! empty( $qv['post_type'] ) ) {
			if ( is_array( $qv['post_type'] ) ) {
				$qv['post_type'] = array_map( 'sanitize_key', $qv['post_type'] );
			} else {
				$qv['post_type'] = sanitize_key( $qv['post_type'] );
			}
		}

		if ( ! empty( $qv['post_status'] ) ) {
			if ( is_array( $qv['post_status'] ) ) {
				$qv['post_status'] = array_map( 'sanitize_key', $qv['post_status'] );
			} else {
				$qv['post_status'] = preg_replace( '|[^a-z0-9_,-]|', '', $qv['post_status'] );
			}
		}

		if ( $this->is_posts_page && ( ! isset( $qv['withcomments'] ) || ! $qv['withcomments'] ) ) {
			$this->is_comment_feed = false;
		}

		$this->is_singular = $this->is_single || $this->is_page || $this->is_attachment;
		// Done correcting `is_*` for 'page_on_front' and 'page_for_posts'.

		if ( '404' == $qv['error'] ) {
			$this->set_404();
		}

		$this->is_embed = $this->is_embed && ( $this->is_singular || $this->is_404 );

		$this->query_vars_hash    = md5( serialize( $this->query_vars ) );
		$this->query_vars_changed = false;

		/**
		 * Fires after the main query vars have been parsed.
		 *
		 * @since 1.5.0
		 *
		 * @param WP_Query $this The WP_Query instance (passed by reference).
		 */
		do_action_ref_array( 'parse_query', array( &$this ) );
	}