How Have Enumerations in PHP Evolved, and What Workarounds Existed Before Native Support?

Enumerations on PHP

PHP natively lacked enumerations until version 8.1, making it difficult to store predefined values. A popular solution was to use constants, but they suffered from namespace collision issues and global scope. Arrays, while immune to namespace collisions, lacked type safety and were prone to runtime overwrites.

Native Enumerations in PHP 8.1

Since PHP 8.1, native enumerations have been introduced. They provide a clean syntax for defining enums:

enum DaysOfWeek: int
{
    case Sunday = 0;
    case Monday = 1;
    // ...
}

Enums can be used for type-safe constants and value validation:

$today = DaysOfWeek::Sunday;
if ($today === DaysOfWeek::Monday) {
    // ...
}

Workarounds for PHP 8.0 and Earlier

Prior to PHP 8.1, popular workarounds included:

• Abstract Enum Classes: Define an abstract class with consts representing enum values:

abstract class DaysOfWeek
{
    const Sunday = 0;
    const Monday = 1;
    // ...
}

• Enhanced Enum Classes: Extend BasicEnum to provide validation methods:

abstract class BasicEnum {}

abstract class DaysOfWeek extends BasicEnum
{
    const Sunday = 0;
    const Monday = 1;
    // ...
}

With these classes, value validation becomes possible:

if (DaysOfWeek::isValidName('Monday')) {
    // ...
}

Other Options

• SplEnum: This class can be used to create enum instances, but it is not as widely accepted as the above approaches.
• External Libraries: Some external libraries also offer enum support.

Conclusion

With the introduction of native enumerations in PHP 8.1, working with predefined values has become easier and more robust. However, even for older PHP versions, there are effective workarounds available to provide enum-like functionality.

The above is the detailed content of How Have Enumerations in PHP Evolved, and What Workarounds Existed Before Native Support?. For more information, please follow other related articles on the PHP Chinese website!