Uncaught TypeError: Trongate_pages::set_per_page(): Argument #1 ($selected_index) must be of type int, string given

if (!is_numeric($selected_index)) {
<br> $selected_index = $this-&gt;per_page_options[1];
<br> }

/**
<br> * Set the number of items per page based on the selected index.
<br> *
<br> * @return void
<br> */
<br> function set_per_page($selected_index): void {
<br> $this-&gt;module('trongate_security');
<br> $this-&gt;trongate_security-&gt;_make_sure_allowed();
<br>
<br> $_SESSION['selected_per_page'] = (int)$selected_index;
<br> redirect('trongate_pages/manage');
<br> }

/**
<br> * Set the number of items per page based on the selected index.
<br> *
<br> * @return void
<br> */
<br> function set_per_page($selected_index): void {
<br> $this-&gt;module('trongate_security');
<br> $this-&gt;trongate_security-&gt;_make_sure_allowed();
<br> $_SESSION['selected_per_page'] = $this-&gt;per_page_options[(int)$selected_index];
<br> redirect('trongate_pages/manage');
<br> }

/**
<br> * Get the number of records selected per page.
<br> *
<br> * @return int The number of records selected per page.
<br> */
<br> function _get_selected_per_page(): int {
<br> $selected_per_page = (isset($_SESSION['selected_per_page'])) ? array_search($_SESSION['selected_per_page'], $this-&gt;per_page_options) : 1;
<br> return $selected_per_page;
<br> }