Joomla中双冒号和下划线的含义是什么？

Question

I am learning basic PHP, trying to read and get some basic understanding of JOOMLA core files, whereas I come across a lot of operators like "::_", which I don't understand.

I did some google research and there are a lot of explanations regarding double colons (::), but almost nothing on "::_", one of the files that contain this operator is joomla-site-root/mod_login/tmpl/default.php, and the line is

<form action="<?php echo JRoute::_('index.php', true, $params->get('usesecure')); ?>" method="post" id="login-form">

So what does this mean? Is "JRoute::_('index.php', true, $params->get('usesecure'))" a function call of class JRoute? if yes, what function is it? I checked out the joomla API(http://api.joomla.org/Joomla-Platform/Application/JRouter.html) but still remain clueless. Please, any help would be greatly appreciated.

Answer 1

The double colon is called the scope resolution operator and is used for calling static class methods or properties. Underscore doesnt mean anything but _() is usually used for string translations.