Enumerations on PHP

Question 1

I know that PHP doesn't yet have native Enumerations. But I have become accustomed to them from the Java world. I would love to use enums as a way to give predefined values which IDEs' auto-completion features could understand.

Constants do the trick, but there's the namespace collision problem and (or actually because) they're global. Arrays don't have the namespace problem, but they're too vague, they can be overwritten at runtime and IDEs rarely know how to autofill their keys without additional static analysis annotations or attributes.

Are there any solutions/workarounds you commonly use? Does anyone recall whether the PHP guys have had any thoughts or decisions around enumerations?

Question 2

Depending upon use case, I would normally use something simple like the following:

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

$today = DaysOfWeek::Sunday;

However, other use cases may require more validation of constants and values. Based on the comments below about reflection, and a few other notes, here's an expanded example which may better serve a much wider range of cases:

abstract class BasicEnum {
    private static $constCacheArray = NULL;

    private static function getConstants() {
        if (self::$constCacheArray == NULL) {
            self::$constCacheArray = [];
        }
        $calledClass = get_called_class();
        if (!array_key_exists($calledClass, self::$constCacheArray)) {
            $reflect = new ReflectionClass($calledClass);
            self::$constCacheArray[$calledClass] = $reflect->getConstants();
        }
        return self::$constCacheArray[$calledClass];
    }

    public static function isValidName($name, $strict = false) {
        $constants = self::getConstants();

        if ($strict) {
            return array_key_exists($name, $constants);
        }

        $keys = array_map('strtolower', array_keys($constants));
        return in_array(strtolower($name), $keys);
    }

    public static function isValidValue($value, $strict = true) {
        $values = array_values(self::getConstants());
        return in_array($value, $values, $strict);
    }
}

By creating a simple enum class that extends BasicEnum, you now have the ability to use methods thusly for simple input validation:

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

DaysOfWeek::isValidName('Humpday');                  // false
DaysOfWeek::isValidName('Monday');                   // true
DaysOfWeek::isValidName('monday');                   // true
DaysOfWeek::isValidName('monday', $strict = true);   // false
DaysOfWeek::isValidName(0);                          // false

DaysOfWeek::isValidValue(0);                         // true
DaysOfWeek::isValidValue(5);                         // true
DaysOfWeek::isValidValue(7);                         // false
DaysOfWeek::isValidValue('Friday');                  // false

As a side note, any time I use reflection at least once on a static/const class where the data won't change (such as in an enum), I cache the results of those reflection calls, since using fresh reflection objects each time will eventually have a noticeable performance impact (Stored in an assocciative array for multiple enums).

Now that most people have finally upgraded to at least 5.3, and SplEnum is available, that is certainly a viable option as well--as long as you don't mind the traditionally unintuitive notion of having actual enum instantiations throughout your codebase. In the above example, BasicEnum and DaysOfWeek cannot be instantiated at all, nor should they be.

Question 3

Try either

sudo apt-get install php-zip or
sudo apt-get install php5.6-zip

Then, you might have to restart your web server.

sudo service apache2 restart or
sudo service nginx restart

If you are installing on centos or fedora OS then use yum in place of apt-get. example:-

sudo yum install php-zip or sudo yum install php5.6-zip and sudo service httpd restart

Question 4

The answer to the question is: No. You can't use a variable from Javascript inside PHP. You can generate valid Javascript code with PHP, but not the other way around. The reason is that PHP is processed in the server side, while Javascript is processed on the client side (the browser)

NOTE: You can process Javascript on the server side as well using Node, but you are already using PHP. How to use server side javascript with NodeJs is out of the scope of the question.

Now, you can create that table with PHP, and not use JS at all. I'm assuming your data is in an array format, so look into PHP loops like foreach. Then build a table by echoing (see echo('')) the table tags (table, thead, tbody, td, tr, etc).

Question 5

Looking at the Java API Specification for the Iterator interface, there is an explanation of the differences between Enumeration:

Iterators differ from enumerations in two ways:

Iterators allow the caller to remove elements from the underlying collection during the iteration with well-defined semantics.

Method names have been improved.

The bottom line is, both Enumeration and Iterator will give successive elements, but Iterator improved the method names by shortening away the verbiage, and it has an additional remove method. Here is a side-by-side comparison:

  Enumeration                     Iterator
  ----------------                ----------------
  hasMoreElements()               hasNext()
  nextElement()                   next()
  N/A                             remove()

As also mentioned in the Java API Specifications, for newer programs, Iterator should be preferred over Enumeration, as "Iterator takes the place of Enumeration in the Java collections framework." (From the Iterator specifications.)

Question 6

Never used any of those, but they look interesting..

Take a look at Gearman as well.. more overhead in systems like these but you get other cool stuff :) Guess it depends on your needs ..

Enumerations on PHP

Answers

php,enumeration