Repository pattern in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the Repository interface.

PHP

<?php
interface [1] {
    public function findAll();
}

Drag options to blanks, or click blank then click option'

AController

BDatabase

CService

DRepository

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated names like Service or Controller for the interface.

The interface is named Repository to define the contract for data access.

2fill in blank

medium

Complete the method signature to find an item by its ID.

PHP

<?php
interface Repository {
    public function findById([1] $id);
}

Drag options to blanks, or click blank then click option'

Astring

Bint

Cbool

Darray

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect types like bool or array for the ID parameter.

The findById method usually takes an int as the ID parameter.

3fill in blank

hard

Fix the error in the repository implementation class declaration.

PHP

<?php
class UserRepository [1] Repository {
    public function findAll() {
        // code to get all users
    }
}

Drag options to blanks, or click blank then click option'

Auses

Bextends

Cimplements

Dinherits

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'extends' keyword for interfaces causes errors.

In PHP, classes implement interfaces using the implements keyword.

4fill in blank

hard

Fill both blanks to complete the method that saves a user entity.

PHP

<?php
class UserRepository implements Repository {
    public function save([1] $user) : [2] {
        // code to save user
    }
}

Drag options to blanks, or click blank then click option'

AUser

Bbool

Cvoid

Darray

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter types or return types like void or array.

The save method takes a User object and returns a bool indicating success.

5fill in blank

hard

Fill all three blanks to complete the repository method that deletes a user by ID.

PHP

<?php
class UserRepository implements Repository {
    public function delete([1] $id) : [2] {
        // code to delete user
        return [3];
    }
}

Drag options to blanks, or click blank then click option'

Aint

Bbool

Ctrue

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong types or returning false by default.

The delete method takes an int ID, returns a bool, and returns true on success.

Practice

1. What is the main purpose of the Repository pattern in PHP?

easy

A. To separate data access logic from business logic

B. To directly connect the database with the user interface

C. To write all code inside a single class

D. To avoid using interfaces in the code

Solution

1. Step 1: Understand the role of Repository pattern

   The Repository pattern is designed to separate how data is accessed from how the business logic works.

2. Step 2: Identify the correct purpose

   Separating data access from business logic makes code cleaner and easier to maintain.

3. Final Answer:

   To separate data access logic from business logic -> Option A

4. Quick Check:

   Repository pattern = separation of concerns [OK]

Hint: Remember: Repository separates data logic from business logic [OK]

Common Mistakes:

• Thinking Repository connects UI directly to database
• Believing all code should be in one class
• Ignoring the use of interfaces

2. Which of the following is the correct way to declare a Repository interface in PHP?

easy

A. UserRepository interface { public function findUser(int $id); }

B. class UserRepository { public function findUser(int $id); }

C. interface UserRepository { function findUser; }

D. interface UserRepository { public function findUser(int $id); }

Solution

1. Step 1: Recall PHP interface syntax

   Interfaces use the keyword interface followed by method declarations with parentheses and types.

2. Step 2: Check each option

   interface UserRepository { public function findUser(int $id); } correctly declares an interface with a method having a typed parameter. class UserRepository { public function findUser(int $id); } uses class instead of interface. interface UserRepository { function findUser; } misses parentheses. UserRepository interface { public function findUser(int $id); } has wrong syntax order.

3. Final Answer:

   interface UserRepository { public function findUser(int $id); } -> Option D

4. Quick Check:

   Interface syntax = interface UserRepository { public function findUser(int $id); } [OK]

Hint: Interfaces use 'interface' keyword and method signatures with parentheses [OK]

Common Mistakes:

• Using 'class' instead of 'interface'
• Omitting parentheses in method declaration
• Wrong keyword order in interface declaration

3. Given the following PHP code, what will be the output?

interface UserRepository {
    public function findUser(int $id);
}

class UserRepo implements UserRepository {
    public function findUser(int $id) {
        return "User_" . $id;
    }
}

$repo = new UserRepo();
echo $repo->findUser(5);

medium

A. 5

B. User_5

C. UserRepo

D. Error: Interface method not implemented

Solution

1. Step 1: Understand interface and class implementation

   The class UserRepo implements UserRepository and defines the method findUser that returns "User_" concatenated with the id.

2. Step 2: Trace the method call

   Calling $repo->findUser(5) returns "User_5" which is then printed.

3. Final Answer:

   User_5 -> Option B

4. Quick Check:

   Method returns 'User_' + id = User_5 [OK]

Hint: Look for string concatenation in method return [OK]

Common Mistakes:

• Expecting just the number 5 as output
• Confusing class name with output
• Thinking interface causes error if implemented correctly

4. Identify the error in this PHP Repository implementation:

interface ProductRepository {
    public function getProduct(int $id);
}

class ProductRepo implements ProductRepository {
    public function getProduct() {
        return "Product";
    }
}

medium

A. Class name should be ProductRepository, not ProductRepo

B. Interface keyword is misspelled

C. Method getProduct() missing parameter in class implementation

D. Return type is missing in interface method

Solution

1. Step 1: Compare interface and class method signatures

   The interface method getProduct requires an int $id parameter, but the class method has no parameters.

2. Step 2: Understand PHP interface implementation rules

   When implementing an interface, method signatures must match exactly, including parameters.

3. Final Answer:

   Method getProduct() missing parameter in class implementation -> Option C

4. Quick Check:

   Method signatures must match [OK]

Hint: Check method parameters match interface exactly [OK]

Common Mistakes:

• Ignoring parameter mismatch
• Thinking class name must match interface name
• Assuming return type is mandatory in interface

5. You want to create a flexible Repository pattern for managing users and products. Which design approach best supports adding new data types without changing existing code?

hard

A. Create separate interfaces like UserRepository and ProductRepository, then implement them in separate classes

B. Write one big class handling all data types with many methods

C. Use global functions to access data directly

D. Store all data in arrays inside a single class without interfaces

Solution

1. Step 1: Understand flexibility in Repository pattern

   Using separate interfaces and classes for each data type allows adding new repositories without changing existing ones.

2. Step 2: Evaluate options for maintainability

   Create separate interfaces like UserRepository and ProductRepository, then implement them in separate classes supports open/closed principle: open for extension, closed for modification. Other options mix concerns or lack structure.

3. Final Answer:

   Create separate interfaces like UserRepository and ProductRepository, then implement them in separate classes -> Option A

4. Quick Check:

   Separate interfaces = flexible extension [OK]

Hint: Use separate interfaces and classes for each data type [OK]

Common Mistakes:

• Putting all logic in one big class
• Using global functions instead of classes
• Avoiding interfaces reduces flexibility