WordPress at a glance
function is not described

_wp_expand_nav_menu_post_data() WP 4.5.3

If a JSON blob of navigation menu data is in POST data, expand it and inject it into $_POST to avoid PHP max_input_vars limitations. See #14134.

No Hooks.

Return

Nothing (null).

Usage

_wp_expand_nav_menu_post_data();

Code of wp expand nav menu post data: wp-admin/includes/nav-menu.php WP 5.2.2

<?php
function _wp_expand_nav_menu_post_data() {
	if ( ! isset( $_POST['nav-menu-data'] ) ) {
		return;
	}

	$data = json_decode( stripslashes( $_POST['nav-menu-data'] ) );

	if ( ! is_null( $data ) && $data ) {
		foreach ( $data as $post_input_data ) {
			// For input names that are arrays (e.g. `menu-item-db-id[3][4][5]`),
			// derive the array path keys via regex and set the value in $_POST.
			preg_match( '#([^\[]*)(\[(.+)\])?#', $post_input_data->name, $matches );

			$array_bits = array( $matches[1] );

			if ( isset( $matches[3] ) ) {
				$array_bits = array_merge( $array_bits, explode( '][', $matches[3] ) );
			}

			$new_post_data = array();

			// Build the new array value from leaf to trunk.
			for ( $i = count( $array_bits ) - 1; $i >= 0; $i -- ) {
				if ( $i == count( $array_bits ) - 1 ) {
					$new_post_data[ $array_bits[ $i ] ] = wp_slash( $post_input_data->value );
				} else {
					$new_post_data = array( $array_bits[ $i ] => $new_post_data );
				}
			}

			$_POST = array_replace_recursive( $_POST, $new_post_data );
		}
	}
}