Enum backed values in PHP - Step-by-Step Execution

Concept Flow - Enum backed values

Define Enum with backed values

↓

Create Enum instance

↓

Access backed value

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Use value in code

This flow shows how to define an enum with values, create an instance, and access its backed value.

Execution Sample

PHP

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

echo Status::Approved->value;
?>

Defines a string-backed enum Status and prints the value of the Approved case.

Execution Table

Step	Action	Evaluation	Result
1	Define enum Status with cases and backed string values	N/A	Enum Status created with cases Pending, Approved, Rejected
2	Access Status::Approved	Status::Approved	Enum case Approved selected
3	Get value of Status::Approved	Status::Approved->value	'approved'
4	Print value	echo Status::Approved->value	Output: approved
5	End of script	N/A	Script ends

💡 Script ends after printing the backed value of the Approved enum case.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
Status::Approved	N/A	Enum case object	Enum case object with value 'approved'	Enum case object with value 'approved'
Output	N/A	N/A	N/A	'approved'

Key Moments - 2 Insights

Why do we use ->value after the enum case?

The ->value accesses the backed value of the enum case, as shown in execution_table step 3 where Status::Approved->value returns 'approved'.

Can enum cases have different types of backed values?

Yes, enums can be backed by strings or integers, but all cases must use the same type, as shown in the enum definition in execution_table step 1.

Visual Quiz - 3 Questions

Look at the execution table, what is the output printed at step 4?

A 'pending'

B 'approved'

C 'Approved'

D No output

💡 Hint

Check the 'Result' column at step 4 in the execution_table.

At which step is the enum case Status::Approved selected?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column to find when Status::Approved is accessed.

If we changed the enum to use integers instead of strings, what would change in the execution_table?

A The output would be the same string values

B The enum cases would not be accessible

C The backed values in step 3 would be integers instead of strings

D The script would fail to run

💡 Hint

Refer to the 'Evaluation' and 'Result' columns in step 3 about backed values.

Concept Snapshot

PHP Enum backed values:
- Define enum with 'enum Name: type { case A = value; }'
- Backed types: string or int
- Access value with 'EnumCase->value'
- Useful for fixed sets with known values
- Example: enum Status: string { case Pending = 'pending'; }

Full Transcript

This example shows how to define a PHP enum with backed string values. The enum Status has three cases: Pending, Approved, and Rejected, each with a string value. When we access Status::Approved and then use ->value, we get the string 'approved'. The script prints this value. The execution table traces each step: defining the enum, selecting the case, getting the value, printing it, and ending the script. Variables track the enum case object and the output string. Key points include why ->value is needed to get the backed value and that all enum cases share the same backed type. The quiz tests understanding of output, step actions, and what changes if the backed type changes.