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WordPress

get_main_site_id( int $network_id = null ): int

Since
4.9.0
Source
wp-includes/functions.php:6423
Gets the main site ID.

Compatibility

WordPress
since 4.9.0
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.

Parameters

$network_idintoptional
The ID of the network for which to get the main site.
Defaults to the current network.Default: null

Return value

int
The ID of the main site.

Performance profile

How much work a call to get_main_site_id() 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
Trivial

Touches nothing outside its own arguments.

Scaling
Constant

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

Instructions
7–11

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 15.

Plugin surface
None

Nothing here hands control to plugin code.

Called by
2

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

What it touches

  • hookthird-party callbacksapply_filters()one call below get_main_site_id()

What one call costs · 2 distinct outcomes

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

WhenInstructionsCalls it makes
!is_multisite()7is_multisite(), get_current_blog_id()
is_multisite()10–11is_multisite(), get_network()

Across PHP versions

Compiles the same on PHP 7.4, 8.1, 8.2, 8.3, 8.4, 8.5 and 8.6-dev: 15 instructions, 7–11 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 · 3

Used by · 2

  • is_main_site()Determines whether a site is the main site of the current network.
  • ms_load_current_site_and_network()Identifies the network and site of a requested domain and path and populates the corresponding network and site global objects as part of the multisite bootstrap process.

Source code

View on Trac View on GitHub 

function get_main_site_id( $network_id = null ) {	if ( ! is_multisite() ) {		return get_current_blog_id();	} 	$network = get_network( $network_id );	if ( ! $network ) {		return 0;	} 	return $network->site_id;}

Changelog

Introduced in 4.9.0. 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 6.8.8 tag, from src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.
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