Top 10 Codeigniter Interview Questions for Experienced

What is hook?

CodeIgniter’s Hooks feature modify the core functionalities of the framework without changing the core files. For example, If you want to run a script right before your controllers get loaded, or right after or at any other location, you can use Hook.

How many types of hooks are there in Code Igniter?

There are 7 available hook points:

pre_system

Called very early during system execution. Only the benchmark and hooks class have been loaded at this point. No routing or other processes have happened.

pre_controller

Called prior to controllers being called. All base classes, routing, and security checks have been done

post_controller_constructor

Called after controller is instantiated, but prior to any method calls happening.

post_controller

Called after the controller is executed.

display_override

Overrides the _display() method, used to send the finalised page to the web browser at the end of system execution. This permits you to use your own display methodology.

Note that you will need to reference the CI super object with $this->CI->get_instance() and then the finalised data will be available by calling $this->CI->output->get_output().

cache_override:

Enables you to call your own method instead of the _display_cache() method in the Output Library. This permits you to use your own cache display mechanism.

post_system:

Called after the final rendered page is sent to the browser, at the end of system execution after the finalised data is sent to the browser.

How to Create a Hook in CodeIgniter?

&amp;lt;?php 
$my_hook = array(
    'class' =&amp;gt; 'YourClassname',
    'function' =&amp;gt; 'your_function_name',
    'filename' =&amp;gt; 'your_filename.php',
    'params' =&amp;gt; array('p1', 'p2'),
    'filepath' =&amp;gt; 'hooks'
);
$hook['pre_controller'] = $my_hook;
?&amp;gt;

Can we use multiple call to same hook?

Yes , we can use multiple call to same hook. Then We have to use multidimensional array:

$hook[‘pre_controller’][]= $hook_one;

$hook[‘pre_controller’][]= $hook_two;

What are the benefits of using hook in an application?

-We can modify core functionalities without touching the core files.

-We can generate desired output without changing the view files.

-we can make a hook for recurring calls , like including footer and header in each function, without calling them in each controller function.

-we can create a script to minify the code before execution take place.

-We can easily implement security checks, privacy, session, cache using hooks and can separate these implementation from the main functionalities.

What is HMVC?

HMVC is a Modular version of MVC. In this system we can implement modules for particular purpose. We may have put out controller , views and model in different modules. All these modules will be available in modules folder in application. HMVC stands for Hierarchical Model View Controller.

What is a module?

A module is a part of application and a full featured block which is implemented on HMVC pattern. A module contains its own Model, View and Controller. Although these resources can be shared with other modules.

What is difference between Library and Helper?

A CodeIgniter helper is a set of related global functions, you can call them any where in application. Once you load the helper file you can directly call the function. Basically the helper is procedural.

But a Library is a class, which you need to make an instance of the class. Once the library is loaded, we need to use $this operator to call the Library function. This is Object Oriented.

What is Routes in Code Igniter Framework?

Routing is the communication between URI and Controller. Routing decides the controller calls and parameters in code igniter. We can overwrite the routing rules in routes.php file.

How to use or enable libraries CodeIgniter?

We can initialise the library in controllers as given below:

$this->load->library('my_library_class');

Why CodeIgniter is a loosely coupled MCV framework?

CodeIgniter is called a loosely coupled mvc because, it provides unlimited flexibility to developers. It allows us to write and execute our custom codes, library, helpers. We can use call model and controllers functions in views and also can write custom code on views. It works like a core php when some one is going to manipulate it and on the other side it provide a modular structure to our application, XSS and CSRF functionalities. It provides us lots of inbuilt library and also compatible with many more custom libraries. It never restricts us to write and execute any code.