如何创建可以访问其函数名称的帮助程序

This my library filename: MY_is_date_helper.php

function is_date($date){
    $d = DateTime::createFromFormat('Y-m-d', $date);
    return $d && $d->format('Y-m-d') == $date;
}

My question is how can I call it to my MVC using just like this:

is_date('2000-01-01');

like what the base_url() did without creating any file at the system folder.

Thanks in advance.

Save file in application/helpers dir

Then you need to load your helper in controller like

$this->load->helper('MY_is_date_helper');

Or add it to autoload in config

$autoload['helper'] = array('MY_is_date_helper');

You can do this in your current php file where you want to use finction -

<?php
    include 'MY_is_date_helper.php';

    is_date('2000-01-01'); // call function
?>