WordPress at a glance
function is not described

avoid_blog_page_permalink_collision() WP 3.0.0

Avoids a collision between a site slug and a permalink slug.

In a subdirectory installation this will make sure that a site and a post do not use the same subdirectory by checking for a site with the same name as a new post.

No Hooks.

Return

Array. The new array of post data after checking for collisions.

Usage

avoid_blog_page_permalink_collision( $data, $postarr );
$data(array) (required)
An array of post data.
$postarr(array) (required)
An array of posts. Not currently used.

Code of avoid blog page permalink collision: wp-admin/includes/ms.php WP 5.2.2

<?php
function avoid_blog_page_permalink_collision( $data, $postarr ) {
	if ( is_subdomain_install() ) {
		return $data;
	}
	if ( $data['post_type'] != 'page' ) {
		return $data;
	}
	if ( ! isset( $data['post_name'] ) || $data['post_name'] == '' ) {
		return $data;
	}
	if ( ! is_main_site() ) {
		return $data;
	}

	$post_name = $data['post_name'];
	$c         = 0;
	while ( $c < 10 && get_id_from_blogname( $post_name ) ) {
		$post_name .= mt_rand( 1, 10 );
		$c ++;
	}
	if ( $post_name != $data['post_name'] ) {
		$data['post_name'] = $post_name;
	}
	return $data;
}