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apply_filters( 'pre_get_main_site_id', int|null $main_site_id, WP_Network $network )

Filters the main site ID.

Returning a positive integer will effectively short-circuit the function.

$main_site_id: (int|null) If a positive integer is returned, it is interpreted as the main site ID.
$network: (WP_Network) The network object for which the main site was detected.

Used By	Description
wp-includes/class-wp-network.php: WP_Network::get_main_site_id()	Returns the main site ID for the network.

Version	Description
4.9.0	Introduced.

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Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/hooks/pre_get_main_site_id