PHP Basics in OpenCart $_[']

PHP Basic issues within OpenCart $_[']
PHP code in the language pack:
$_[' heading_title ']= ' hello ';

Controller:
$this->data[' heading_title ']= $this->language->get (' Heading_title ');
View:
will become Hello

Here, the hello in the language pack is passed to the variable $heading_titile in the view;
What do you mean by "$_[" here? Why can I use get (' heading_title ') to get ' hello ' why can I say $_?

------Solution--------------------
$_ is the variable name

As for why you can use Get (' heading_title ') to get ' Hello
You can refer to its documentation.
------Solution--------------------
Language is an object that you say the language pack
$this->language->get (' Heading_title ') when language packs are accessed
The actual access is $_[' Heading_title ']
Internal implementation Please analyze the relevant code

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