MVC architecture overview in PHP - Step-by-Step Execution

Concept Flow - MVC architecture overview

User Request

↓

Controller receives request

↓

Controller processes input

↓

Controller calls Model

↓

Model handles data and logic

↓

Model returns data to Controller

↓

Controller sends data to View

↓

View renders output

↓

Response sent to User

The MVC flow starts with a user request handled by the Controller, which uses the Model for data and logic, then passes results to the View to create the output.

Execution Sample

PHP

<?php
// Controller receives request
class Controller {
  public function show() {
    $data = Model::getData();
    View::render($data);
  }
}
?>

This simple PHP code shows the Controller calling the Model to get data, then passing it to the View to display.

Execution Table

Step	Action	Component	Data/State	Output
1	User sends request	User	Request URL: /show	Request received by Controller
2	Controller receives request	Controller	Method: show()	Calls Model::getData()
3	Model processes data	Model	Fetch data from DB or logic	Returns data array ['name' => 'Alice']
4	Controller receives data	Controller	Data: ['name' => 'Alice']	Calls View::render(data)
5	View renders output	View	Data: ['name' => 'Alice']	HTML page with 'Hello, Alice!'
6	Response sent	System	Rendered HTML	User sees page
7	End	System	Request complete	Execution stops

💡 Request handled fully; response sent to user, execution ends.

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
request	null	/show	/show	/show
data	null	['name' => 'Alice']	['name' => 'Alice']	['name' => 'Alice']
output	null	null	null	HTML with 'Hello, Alice!'

Key Moments - 3 Insights

Why does the Controller call the Model before the View?

The Controller calls the Model first to get the data needed. Then it passes that data to the View to display. This order is shown in steps 3 and 4 of the execution table.

Does the View access the Model directly?

No, the View only receives data from the Controller. It does not call the Model. This separation keeps the code organized, as seen in step 5.

What happens after the View renders the output?

After rendering, the output is sent back to the user as a response, ending the request cycle. This is shown in step 6 and 7.

Visual Quiz - 3 Questions

Look at the execution table, at which step does the Model return data to the Controller?

A Step 4

B Step 3

C Step 5

D Step 2

💡 Hint

Check the 'Action' and 'Output' columns in step 3 where Model returns data.

At which step does the View create the HTML output?

A Step 2

B Step 4

C Step 5

D Step 6

💡 Hint

Look for 'View renders output' in the 'Action' column.

If the Controller skipped calling the Model, what would happen in the execution table?

A Data would be null or missing at step 4

B View would render normally with data

C User request would be sent twice

D Model would still send data automatically

💡 Hint

Refer to variable_tracker for 'data' variable changes after step 3 and 4.

Concept Snapshot

MVC Architecture Overview:
- Model: Manages data and logic
- View: Displays data to user
- Controller: Handles user input, calls Model, sends data to View
- Flow: User -> Controller -> Model -> Controller -> View -> User
- Keeps code organized and separates concerns

Full Transcript

MVC architecture divides a web app into three parts: Model, View, and Controller. When a user sends a request, the Controller receives it and processes input. The Controller calls the Model to get or update data. The Model handles data logic and returns results. The Controller then sends this data to the View. The View creates the HTML output shown to the user. This flow keeps the app organized and easier to maintain.

Practice

1. In the MVC architecture, which component is responsible for handling user input and updating the model?

easy

A. Controller

B. Model

C. View

D. Database

Solution

1. Step 1: Understand MVC roles

   The Model manages data, the View displays data, and the Controller handles user input.

2. Step 2: Identify the component for user input

   The Controller receives user actions and updates the Model accordingly.

3. Final Answer:

   Controller -> Option A

4. Quick Check:

   Controller handles input [OK]

Hint: Controller connects user actions to data changes [OK]

Common Mistakes:

• Confusing Model with Controller
• Thinking View handles input
• Assuming Database is part of MVC

2. Which of the following is the correct way to describe the role of the Model in MVC?

easy

A. It processes user input and updates views.

B. It manages the data and business logic.

C. It displays data to the user.

D. It handles routing and URLs.

Solution

1. Step 1: Recall Model's responsibility

   The Model stores and manages data and business rules.

2. Step 2: Match description to Model

   Only It manages the data and business logic. correctly states that the Model manages data and logic.

3. Final Answer:

   It manages the data and business logic. -> Option B

4. Quick Check:

   Model manages data and logic [OK]

Hint: Model is about data and rules, not display or input [OK]

Common Mistakes:

• Mixing up Model and View roles
• Thinking Controller manages data
• Confusing routing with Model

3. Given this PHP MVC snippet:

<?php
class Controller {
  public function show() {
    $data = Model::getData();
    View::render($data);
  }
}

class Model {
  public static function getData() {
    return ['name' => 'Alice'];
  }
}

class View {
  public static function render($data) {
    echo 'Hello, ' . $data['name'];
  }
}

$controller = new Controller();
$controller->show();
?>

What is the output when this code runs?

medium

A. Hello, name

B. Array

C. Hello, Alice

D. Error: Undefined index

Solution

1. Step 1: Trace data flow in code

   The Controller calls Model::getData(), which returns ['name' => 'Alice'].

2. Step 2: Check View rendering

   View::render() echoes 'Hello, ' plus the value of $data['name'], which is 'Alice'.

3. Final Answer:

   Hello, Alice -> Option C

4. Quick Check:

   Output = 'Hello, Alice' [OK]

Hint: Follow data from Model to View for output [OK]

Common Mistakes:

• Printing the array directly
• Using wrong array key
• Confusing static method calls

4. Identify the error in this MVC PHP code snippet:

<?php
class Controller {
  public function display() {
    $data = Model::fetchData();
    View::show($data);
  }
}

class Model {
  public static function getData() {
    return ['age' => 30];
  }
}

class View {
  public static function show($data) {
    echo 'Age: ' . $data['age'];
  }
}

$controller = new Controller();
$controller->display();
?>

medium

A. Model::fetchData() method does not exist

B. View::show() method is missing

C. Controller class is not instantiated

D. Array key 'age' is incorrect

Solution

1. Step 1: Check method calls in Controller

   Controller calls Model::fetchData(), but Model only has getData() method.

2. Step 2: Verify Model methods

   Model::fetchData() does not exist, causing a fatal error.

3. Final Answer:

   Model::fetchData() method does not exist -> Option A

4. Quick Check:

   Model::fetchData() method does not exist [OK]

Hint: Match method names exactly between classes [OK]

Common Mistakes:

• Assuming method names are interchangeable
• Ignoring case sensitivity
• Overlooking missing methods

5. You want to add a feature in your PHP MVC app to display a list of users. Which MVC components should you update and how?

hard

A. Update Model to display list, View to fetch users, Controller to store data

B. Update View to fetch users, Controller to display list, Model to handle input

C. Update Controller to fetch users, Model to display list, View to handle input

D. Update Model to fetch users, Controller to pass data, View to display list

Solution

1. Step 1: Assign responsibilities per MVC

   The Model fetches data, Controller processes logic, View shows output.

2. Step 2: Map feature to components

   Model fetches users, Controller gets data and sends to View, View displays user list.

3. Final Answer:

   Update Model to fetch users, Controller to pass data, View to display list -> Option D

4. Quick Check:

   Model=data, Controller=logic, View=display [OK]

Hint: Model gets data, Controller links, View shows it [OK]

Common Mistakes:

• Letting View fetch data directly
• Making Controller handle display
• Confusing roles of MVC parts