Codeigniter: Get Instance

Question

What is the purpose of "Get Instance" in Codeigniter? How would you explain this to a total beginner?

score 63 · Accepted Answer · edited Jul 16 '15 at 08:50

63

Ok, so everything in CodeIgniter runs through the super-magic $this variable. This only works for classes, as $this basically defines the current class.

Your controller is a class, so $this is there, allowing you to do $this->load->model('whatever');

In models, you are also using a class. It is slightly different here, as $this only contains useful stuff as you are extending from Model. Still, $this is still valid.

When you are using a helper or a library, you need to find that "instance" or $this equivalent.

$ci =& get_instance();

…makes $ci contain the exact same stuff/code/usefulness as $this, even though you are not in a class, or not in a class that inherits it.

That's an explanation for total beginners after 2 pints, so it's either wrong or about right. ;-)

edited Jul 16 '15 at 08:50

Chris Martin

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answered May 12 '10 at 14:35

Phil Sturgeon

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2 pints, eh? Then what is the usefullness of a library/helper? Why not just use models? – Kevin Brown May 12 '10 at 14:38
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Of course seeing as everything is a PHP class you CAN put whatever you like wherever you like. Generally speaking in CodeIgniter it is broken down as "database interaction/business logic" = models, simple functions go in helpers and general classes are libraries. – Phil Sturgeon May 13 '10 at 08:07
@PhilSturgeon great explanation :) – Muhammad Zaman Apr 11 '18 at 12:48
Would expect anything less than 2 pints from Phil :-D – jminkler Dec 03 '18 at 21:49

score 11 · Answer 2 · answered May 12 '10 at 13:58

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It's an implementation of the singleton pattern. Essentially, there is only one instance of the class in question, which is designed to be accessible globally. The get_instance method is static and so provides a way of accessing the instance from anywhere in your code.

answered May 12 '10 at 13:58

Will Vousden

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Not noobish enough. I'm a SUPER NOOB! :) – Kevin Brown May 12 '10 at 14:37
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@Kevin: In that case I recommend you start reading about object-oriented programming (OOP) before delving into a framework that relies upon it! – Will Vousden May 12 '10 at 15:09

Codeigniter: Get Instance

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