WP::send_headers()

Description

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Performance profile

How much work a call to WP::send_headers() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Heavy

Reaches the database via get_post().

Scaling

Scales with input

The body loops, so the work grows with how much data it finds.

Instructions

119–165

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 307.

Plugin surface

2 hooks

Third-party callbacks on 'wp_headers', 'send_headers' run inside this call, and their cost is not bounded by anything here.

Called by

1

1 place in core call this, so the cost is paid more often than your own code shows.

What it touches

• optionoption read or writeget_option()called directly
• hookthird-party callbacksapply_filters()called directly
• cacheobject cachewp_cache_get()one call below WP::send_headers()
• serializeserialisationmaybe_unserialize()one call below WP::send_headers()
• querycontent queryget_post()one call below WP::send_headers()

Further down the call graph this can also reach transient. That is the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 72 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost WP::send_headers() can have, taken from its control-flow graph on PHP 8.5.

This body has more branch combinations than are worth enumerating, so the table covers the outcomes found first rather than every one that exists.

Hooks and filters fired · 2

2 hooks fire while WP::send_headers() runs, in this order:

1. 1
   apply_filters( wp_headers )filterline 563 (+128 into the body)

   Filters the HTTP headers before they're sent to the browser.

2. 2
   do_action( send_headers )actionline 598 (+163 into the body)

   Fires once the requested HTTP headers for caching, content type, etc. have been sent.

Uses · 16

• is_user_logged_in()Determines whether the current visitor is a logged in user.
• wp_get_nocache_headers()Gets the HTTP header information to prevent caching.
• get_option()Retrieves an option value based on an option name.
• get_default_feed()Retrieves the default feed.
• feed_content_type()Returns the content type for specified feed type.
• str_contains()Polyfill for `str_contains()` function added in PHP 8.0.
• mysql2date()Converts given MySQL date string into a different format.
• get_lastpostmodified()Gets the most recent time that a post on the site was modified.
• get_lastcommentmodified()Retrieves the date the last comment was modified.
• wp_unslash()Removes slashes from a string or recursively removes slashes from strings within an array.
• is_singular()Determines whether the query is for an existing single post of any post type (post, attachment, page, custom post types).
• pings_open()Determines whether the current post is open for pings.

Used by · 1

• WP::main()Sets up all of the variables required by the WordPress environment.

Source code

View on Trac ↗View on GitHub ↗

435	public function send_headers() {436		global $wp_query;437 438		$headers       = array();439		$status        = null;440		$exit_required = false;441		$date_format   = 'D, d M Y H:i:s';442 443		if ( is_user_logged_in() ) {444			$headers = array_merge( $headers, wp_get_nocache_headers() );445		} elseif ( ! empty( $_GET['unapproved'] ) && ! empty( $_GET['moderation-hash'] ) ) {446			// Unmoderated comments are only visible for 10 minutes via the moderation hash.447			$expires = 10 * MINUTE_IN_SECONDS;448 449			$headers['Expires']       = gmdate( $date_format, time() + $expires );450			$headers['Cache-Control'] = sprintf(451				'max-age=%d, must-revalidate',452				$expires453			);454		}455		if ( ! empty( $this->query_vars['error'] ) ) {456			$status = (int) $this->query_vars['error'];457 458			if ( 404 === $status ) {459				if ( ! is_user_logged_in() ) {460					$headers = array_merge( $headers, wp_get_nocache_headers() );461				}462 463				$headers['Content-Type'] = get_option( 'html_type' ) . '; charset=' . get_option( 'blog_charset' );464			} elseif ( in_array( $status, array( 403, 500, 502, 503 ), true ) ) {465				$exit_required = true;466			}467		} elseif ( empty( $this->query_vars['feed'] ) ) {468			$headers['Content-Type'] = get_option( 'html_type' ) . '; charset=' . get_option( 'blog_charset' );469		} else {470			// Set the correct content type for feeds.471			$type = $this->query_vars['feed'];472			if ( 'feed' === $this->query_vars['feed'] ) {473				$type = get_default_feed();474			}475 476			$headers['Content-Type'] = feed_content_type( $type ) . '; charset=' . get_option( 'blog_charset' );477 478			// We're showing a feed, so WP is indeed the only thing that last changed.479			if ( ! empty( $this->query_vars['withcomments'] )480				|| str_contains( $this->query_vars['feed'], 'comments-' )481				|| ( empty( $this->query_vars['withoutcomments'] )482					&& ( ! empty( $this->query_vars['p'] )483						|| ! empty( $this->query_vars['name'] )484						|| ! empty( $this->query_vars['page_id'] )485						|| ! empty( $this->query_vars['pagename'] )486						|| ! empty( $this->query_vars['attachment'] )487						|| ! empty( $this->query_vars['attachment_id'] )488					)489				)490			) {491				$wp_last_modified_post    = mysql2date( $date_format, get_lastpostmodified( 'GMT' ), false );492				$wp_last_modified_comment = mysql2date( $date_format, get_lastcommentmodified( 'GMT' ), false );493 494				if ( strtotime( $wp_last_modified_post ) > strtotime( $wp_last_modified_comment ) ) {495					$wp_last_modified = $wp_last_modified_post;496				} else {497					$wp_last_modified = $wp_last_modified_comment;498				}499			} else {500				$wp_last_modified = mysql2date( $date_format, get_lastpostmodified( 'GMT' ), false );501			}502 503			if ( ! $wp_last_modified ) {504				$wp_last_modified = gmdate( $date_format );505			}506 507			$wp_last_modified .= ' GMT';508			$wp_etag           = '"' . md5( $wp_last_modified ) . '"';509 510			$headers['Last-Modified'] = $wp_last_modified;511			$headers['ETag']          = $wp_etag;512 513			// Support for conditional GET.514			if ( isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) ) {

Changelog

Introduced in 2.0.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/class-wp.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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