Returns TRUE for "1", "true", "on" and "yes"; FALSE for "0", "false", "off", "no", and ""; NULL for all other values

cast_boolean.php

<?php
if (!function_exists('cast_boolean')) {
    /**
     * Cast `'true'`, `'false'` etc. to bool.
     * @param mixed $value
     * @return bool
     */
    function cast_boolean($value): bool
    {
        return filter_var($value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE);
    }
}