Enums in PHP - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of backed enum value access

What is the output of this PHP code using backed enums?

PHP

<?php
enum Status: string {
    case Pending = 'pending';
    case Completed = 'completed';
}

echo Status::Completed->value;

A pending

B Completed

C Status::Completed

D completed

💡 Hint

Access the string value of the enum case using ->value.

Backed enums in PHP allow each case to have a scalar value. Accessing ->value returns that scalar, here 'completed'.

❓ Predict Output

intermediate

Output of enum method call

What does this PHP code print when calling a method inside an enum?

PHP

<?php
enum Direction {
    case North;
    case South;
    case East;
    case West;

    public function opposite(): Direction {
        return match($this) {
            Direction::North => Direction::South,
            Direction::South => Direction::North,
            Direction::East => Direction::West,
            Direction::West => Direction::East,
        };
    }
}

echo Direction::East->opposite()->name;

A East

B West

C North

D South

💡 Hint

The opposite of East is West according to the match expression.

The method opposite() returns the enum case opposite to the current one. East's opposite is West, so it prints 'West'.

🔧 Debug

advanced

Identify the error in enum declaration

What error does this PHP code raise when declaring this enum?

PHP

<?php
enum Color {
    case Red = 1;
    case Green = 'green';
    case Blue = 3;
}

A Fatal error: Backed enum cases must have the same scalar type

B No error, code runs fine

C TypeError: Enum case values must be integers

D Syntax error: Missing semicolon after case

💡 Hint

Backed enums require all cases to have the same scalar type.

Backed enums must have all cases with the same scalar type (all int or all string). Mixing int and string causes a fatal error.

📝 Syntax

advanced

Which option causes a syntax error?

Which of these enum declarations will cause a syntax error in PHP?

A enum Status: string { case Active = 'yes'; case Inactive = 'no'; }

B enum Status { case Active; case Inactive; }

C enum Status { case Active; case Inactive }

D enum Status: int { case Active = 1; case Inactive = 0; }

💡 Hint

Check for missing semicolons after case declarations.

Option C misses a semicolon after 'case Inactive', causing a syntax error.

🚀 Application

expert

Number of cases in a backed enum

Given this backed enum, how many cases does it contain?

PHP

<?php
enum HttpStatus: int {
    case OK = 200;
    case Created = 201;
    case Accepted = 202;
    case NoContent = 204;
}

$cases = HttpStatus::cases();
echo count($cases);

A 4

B 0

C 5

D 3

💡 Hint

Count the number of case declarations inside the enum.

The enum defines 4 cases: OK, Created, Accepted, NoContent. The count of cases() returns 4.

Practice

1. What is the main purpose of using enum in PHP?

easy

A. To group related constant values under one name

B. To create a new type of variable that can hold any value

C. To define functions inside classes

D. To declare variables with dynamic types

Solution

1. Step 1: Understand what enums represent

   Enums are used to group related constant values, like fixed options or states.

2. Step 2: Compare with other options

   Other options describe unrelated concepts: variables or functions, not enums.

3. Final Answer:

   To group related constant values under one name -> Option A

4. Quick Check:

   Enums = group constants [OK]

Hint: Enums group fixed options clearly [OK]

Common Mistakes:

• Thinking enums create dynamic variables
• Confusing enums with classes or functions
• Assuming enums can hold any value

2. Which of the following is the correct syntax to declare a backed enum with string values in PHP?

easy

A. enum Status: string { case Active = 'active'; case Inactive = 'inactive'; }

B. enum Status { case Active = 'active'; case Inactive = 'inactive'; }

C. enum Status: int { case Active = 'active'; case Inactive = 'inactive'; }

D. enum Status: string { Active = 'active'; Inactive = 'inactive'; }

Solution

1. Step 1: Identify backed enum syntax

   Backed enums require a type after the enum name, like : string, and cases with assigned values.

2. Step 2: Check each option

   enum Status: string { case Active = 'active'; case Inactive = 'inactive'; } correctly uses enum Status: string { case Active = 'active'; ... }. enum Status { case Active = 'active'; case Inactive = 'inactive'; } misses the type. enum Status: int { case Active = 'active'; case Inactive = 'inactive'; } uses wrong type int with string values. enum Status: string { Active = 'active'; Inactive = 'inactive'; } misses case keyword.

3. Final Answer:

   enum Status: string { case Active = 'active'; case Inactive = 'inactive'; } -> Option A

4. Quick Check:

   Backed enum syntax = enum Status: string { case Active = 'active'; case Inactive = 'inactive'; } [OK]

Hint: Backed enums need type and 'case' keyword [OK]

Common Mistakes:

• Omitting the enum type after colon
• Forgetting 'case' before each value
• Assigning string values to int enums

3. What will be the output of the following PHP code?

enum Direction { case North; case South; case East; case West; }
$dir = Direction::East;
echo $dir->name;

medium

A. Error: Cannot access name

B. direction::East

C. East case

D. East

Solution

1. Step 1: Understand enum case name property

   In PHP enums, $dir->name returns the case name as a string.

2. Step 2: Check the assigned case

   The variable $dir is assigned Direction::East, so $dir->name is "East".

3. Final Answer:

   East -> Option D

4. Quick Check:

   Enum case name = East [OK]

Hint: Use ->name to get enum case name string [OK]

Common Mistakes:

• Expecting the value instead of name
• Trying to print enum case directly
• Confusing case name with enum class name

4. Identify the error in this PHP enum declaration:

enum Color {
  case Red = 1;
  case Green = 2;
  case Blue;
}

medium

A. Case Blue should have a value assigned

B. Missing enum type for backed enum values

C. Enum name must be lowercase

D. Cases cannot have integer values

Solution

1. Step 1: Check enum type for backed values

   When enum cases have assigned values (like 1, 2), the enum must declare a type (e.g., : int).

2. Step 2: Analyze the given enum

   The enum Color assigns values to some cases but does not specify : int after the enum name, causing a syntax error.

3. Final Answer:

   Missing enum type for backed enum values -> Option B

4. Quick Check:

   Backed enums need type declared [OK]

Hint: Backed enums must declare type after enum name [OK]

Common Mistakes:

• Not declaring enum type when assigning values
• Assuming cases can mix assigned and unassigned values
• Thinking enum names must be lowercase

5. Given this enum:

enum Status: string {
  case Pending = 'pending';
  case Approved = 'approved';
  case Rejected = 'rejected';
}

Which code correctly converts a string $input to the matching Status enum case or returns null if no match?

hard

A. new Status($input)

B. Status::from($input)

C. Status::tryFrom($input)

D. Status::$input

Solution

1. Step 1: Understand enum methods for backed enums

   PHP backed enums provide from() which throws error if no match, and tryFrom() which returns null if no match.

2. Step 2: Match requirement

   The question asks to return matching enum or null if no match, so tryFrom() is correct.

3. Final Answer:

   Status::tryFrom($input) -> Option C

4. Quick Check:

   Safe enum conversion = tryFrom() [OK]

Hint: Use tryFrom() to safely convert string to enum [OK]

Common Mistakes:

• Using from() which throws error on no match
• Trying to instantiate enum with new
• Accessing enum cases as static properties