wp-includes/ms-deprecated.php:64Determine if user is a site admin.
$user_loginstringoptional''function is_site_admin( $user_login = '' ) { _deprecated_function( __FUNCTION__, '3.0.0', 'is_super_admin()' ); if ( empty( $user_login ) ) { $user_id = get_current_user_id(); if ( !$user_id ) return false; } else { $user = get_user_by( 'login', $user_login ); if ( ! $user->exists() ) return false; $user_id = $user->ID; } return is_super_admin( $user_id );}Introduced in MU (3.0.0). Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/ms-deprecated.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.