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WordPress

twenty_twenty_one_pingback_header(): void

Since
Twenty Twenty-One 1.0
Source
wp-content/themes/twentytwentyone/inc/template-functions.php:62
Adds a pingback url auto-discovery header for single posts, pages, or attachments.

Compatibility

WordPress
since Twenty Twenty-One 1.0
PHP
7.4–8.6-dev
  • 6.7.7
  • 6.8.8
  • 6.9.7
  • 7.0.4
  • 7.1.0

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

Return value

void

Performance profile

How much work a call to twenty_twenty_one_pingback_header() 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
Constant

No loop in the body: the same number of instructions runs whatever you pass in.

Instructions
4–16

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 16.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
0

Nothing in core calls this; the cost is only what you spend yourself.

What it touches

  • querycontent queryget_post()one call below twenty_twenty_one_pingback_header()
  • hookthird-party callbacksapply_filters()one call below twenty_twenty_one_pingback_header()
  • optionoption read or writeget_option()one call below twenty_twenty_one_pingback_header()

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

What one call costs · 3 distinct outcomes

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

WhenInstructionsCalls it makes
!is_singular()4is_singular()
is_singular() && !pings_open()7is_singular(), pings_open()
is_singular() && pings_open()16is_singular(), pings_open(), get_bloginfo(), esc_url()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 16 instructions, 4–16 executed per call, 2 branches. The work does not change between versions.

An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.

Uses · 4

  • 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.
  • esc_url()Checks and cleans a URL.
  • get_bloginfo()Retrieves information about the current site.

Source code

View on Trac View on GitHub 

function twenty_twenty_one_pingback_header() {	if ( is_singular() && pings_open() ) {		echo '<link rel="pingback" href="', esc_url( get_bloginfo( 'pingback_url' ) ), '">';	}}

Changelog

Introduced in Twenty Twenty-One 1.0. 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-content/themes/twentytwentyone/inc/template-functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
Corrections
Something wrong on this page? Report it and it gets fixed in the next regeneration.