Enum backed values in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a backed enum with string values.

PHP

<?php
enum Status: string {
    case Pending = [1];
    case Approved = 'approved';
    case Rejected = 'rejected';
}

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

Apending

B'pending'

C"pending"

DPending

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around string values

Using unquoted identifiers as values

The backed enum values must be strings enclosed in quotes. So 'pending' is correct.

2fill in blank

medium

Complete the code to get the backed value of the enum case.

PHP

<?php
enum Direction: string {
    case North = 'N';
    case South = 'S';
}

echo Direction::North->[1];

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

Avalue

Bname

CgetValue()

DtoString()

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods like getValue() which do not exist

Using the name property instead of value

In PHP enums, the backed value of a case is accessed using the value property.

3fill in blank

hard

Fix the error in the code to get the enum case from a backed value.

PHP

<?php
enum Status: int {
    case Draft = 0;
    case Published = 1;
}

$status = Status::from([1]);
echo $status->name;

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

A'1'

B"Published"

C1

DPublished

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a string instead of an integer to from()

Passing the case name instead of the backed value

The from method expects the backed value with the correct type. Since the enum is backed by int, use the integer 1, not a string.

4fill in blank

hard

Fill both blanks to create a backed enum and get a case from a backed value.

PHP

<?php
enum Level: [1] {
    case Low = 1;
    case High = 2;
}

echo Level::[2]->value;

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

Aint

BLow

CHigh

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using string as backing type when values are integers

Using the wrong case name

The enum is backed by integers, so use int. To get the value of the Low case, use Level::Low.

5fill in blank

hard

Fill all three blanks to define a backed enum, get a case from a value, and print its name.

PHP

<?php
enum Color: [1] {
    case Red = 'R';
    case Blue = 'B';
    case Green = 'G';
}

$color = Color::from([2]);
echo $color->[3];

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

Astring

B'B'

Cname

Dint

Attempts:

3 left

💡 Hint

Common Mistakes

Using int as backing type when values are strings

Passing unquoted values for string backed enums

Using value property instead of name to print case name

The enum is backed by strings, so use string. To get the case from the backed value 'B', use from('B'). To print the case name, use the name property.

Practice

1.

What is the main purpose of using backed enums in PHP?

easy

A. To allow enums to inherit from classes

B. To link enum cases to fixed strings or numbers

C. To enable enums to have methods

D. To make enums mutable

Solution

1. Step 1: Understand enum backed values

   Backed enums associate each enum case with a fixed string or integer value.

2. Step 2: Identify the purpose

   This linking helps in storing, comparing, or displaying enum data easily.

3. Final Answer:

   To link enum cases to fixed strings or numbers -> Option B

4. Quick Check:

   Backed enums link cases to values = A [OK]

Hint: Backed enums always connect cases to fixed values [OK]

Common Mistakes:

• Thinking enums can inherit classes
• Confusing backed enums with mutable enums
• Assuming enums cannot have methods

2.

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

enum Status: string {
    case ACTIVE = 'active';
    case INACTIVE = 'inactive';
}

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: Check enum declaration syntax

   Backed enums require specifying the type after the enum name, e.g., : string.

2. Step 2: Verify case declarations

   Each case must use the case keyword and assign a value with =.

3. Final Answer:

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

4. Quick Check:

   Backed enum syntax with type and cases = B [OK]

Hint: Backed enums need type after enum name and case keyword [OK]

Common Mistakes:

• Omitting the type after enum name
• Not using 'case' keyword before cases
• Using wrong type like int for string values

3.

What will be the output of the following PHP code?

enum Color: int {
    case RED = 1;
    case GREEN = 2;
    case BLUE = 3;
}

echo Color::from(2)->name;

medium

A. Color::GREEN

B. 2

C. GREEN

D. Error: No case for value 2

Solution

1. Step 1: Understand Color::from(2)

   The from() method returns the enum case matching the value 2, which is GREEN.

2. Step 2: Access the name property

   Using ->name returns the case name as a string, here "GREEN".

3. Final Answer:

   GREEN -> Option C

4. Quick Check:

   from(2) returns GREEN name = GREEN [OK]

Hint: from(value) returns enum case; ->name gives case name [OK]

Common Mistakes:

• Printing the value instead of the name
• Confusing from() with tryFrom()
• Expecting full enum class name output

4.

Identify the error in the following PHP enum backed values code:

enum Status: string {
    case PENDING = 'pending';
    case COMPLETED = 'completed';
}

$status = Status::from('done');

medium

A. No error, code runs fine

B. Compile error: Enum must use int type

C. Syntax error: Missing semicolon after enum cases

D. Runtime error: Value 'done' not found in enum cases

Solution

1. Step 1: Check the from() method usage

   The from() method throws an error if the value does not match any enum case.

2. Step 2: Analyze the value 'done'

   Since 'done' is not a defined case value, a runtime error occurs.

3. Final Answer:

   Runtime error: Value 'done' not found in enum cases -> Option D

4. Quick Check:

   from() with invalid value causes runtime error = D [OK]

Hint: from() fails if value not in enum cases [OK]

Common Mistakes:

• Assuming from() returns null on failure
• Thinking syntax error due to semicolons
• Believing enum must be int type only

5.

Given the following enum, which code snippet correctly converts a string value to an enum case safely without throwing an error?

enum Direction: string {
    case NORTH = 'north';
    case SOUTH = 'south';
    case EAST = 'east';
    case WEST = 'west';
}

Choose the correct usage:

hard

A. $dir = Direction::tryFrom('east');

B. $dir = Direction::from('southwest');

C. $dir = Direction::from('up');

D. $dir = Direction::tryFrom('down');

Solution

1. Step 1: Understand from() vs tryFrom()

   from() throws error if value not found; tryFrom() returns null instead.

2. Step 2: Check each option's value

   Only tryFrom('east') matches a valid case and safely returns the enum case.

3. Final Answer:

   $dir = Direction::tryFrom('east'); -> Option A

4. Quick Check:

   tryFrom() safely converts valid value = C [OK]

Hint: Use tryFrom() to avoid errors on invalid values [OK]

Common Mistakes:

• Using from() with invalid values causing errors
• Expecting tryFrom() to throw errors
• Confusing enum case names with values