WordPress at a glance
function is not described

__checked_selected_helper() WP 2.8.0

Private helper function for checked, selected, disabled and readonly.

Compares the first two arguments and if identical marks as $type

No Hooks.

Return

String. html attribute or empty string

Usage

__checked_selected_helper( $helper, $current, $echo, $type );
$helper(mixed) (required)
One of the values to compare
$current(mixed) (required)
(true) The other value to compare if not just true
$echo(true/false) (required)
Whether to echo or just return the string
$type(string) (required)
The type of checked|selected|disabled|readonly we are doing

Code of checked selected helper: wp-includes/general-template.php WP 5.2.2

<?php
function __checked_selected_helper( $helper, $current, $echo, $type ) {
	if ( (string) $helper === (string) $current ) {
		$result = " $type='$type'";
	} else {
		$result = '';
	}

	if ( $echo ) {
		echo $result;
	}

	return $result;
}