What are the characteristics of enums in PHP?

In PHP, although there is no built-in support for enums, similar functionality can be achieved using the following methods:

1. Use class constants: Define a class containing constants to simulate an enumeration type, where each constant represents an enumeration value.

class Days {
    const Sunday = 0;
    const Monday = 1;
    const Tuesday = 2;
    const Wednesday = 3;
    const Thursday = 4;
    const Friday = 5;
    const Saturday = 6;
}

$day = Days::Monday;
echo $day; // 输出1

1. Utilize the SplEnum class (requires installation of PECL extension): SplEnum is a class provided by a PECL extension that can be used to create enum types.

class Days extends SplEnum {
    const Sunday = 0;
    const Monday = 1;
    const Tuesday = 2;
    const Wednesday = 3;
    const Thursday = 4;
    const Friday = 5;
    const Saturday = 6;
}

$day = new Days(Days::Monday);
echo $day; // 输出1

Although PHP does not have direct support for enumerations, the above two methods can simulate the functionality of enumerations.