When to use method vs setting a property in the constructor? - php

Question

I'm new to OOP, and I'm not sure when I should be setting properties in the constructor for my own convenience, as opposed to just using a method.
Option 1 (method):
class String {
function __construct($word) {
$this->word = $word;
}
function reverse() {
return str_reverse($this->word);
}
}
Then I can get the reverse like this:
$word = new String('potato');
echo $word->reverse();
Option 2 (property):
class String {
public $reverse;
function __construct($word) {
$this->word = $word;
$this->reverse = $this->reverse();
}
function reverse() {
return str_reverse($this->word);
}
}
Then I can get the reverse like this:
$word = new String('potato');
echo $word->reverse;
The second option looks nicer.
However, I was wondering if there are any pitfalls of using Option 2 all the time?

Answer 1

tl;dr
You need to find out for yourself what works best for your context.
Value Object
Here's an example of a value object that might make sense to you:
it holds state
it is immutable
invoking $word->reverse() returns a new instance of a value object, however, with the reversed string value
final class Word
{
private $word;
public function __construct(string $word)
{
$this->word = $word;
}
public function reverse(): self
{
return new self(strrev($this->word));
}
public function __toString()
{
return $this->word;
}
}
$word = new Word('potato');
echo $word->reverse();
For an example, see:
https://3v4l.org/ONklH
Service
Here's an example of a service:
it doesn't hold any state
invoking $service->reverse() requires passing in the word, it returns the word reversed
final class Service
{
public function reverse(string $word): string
{
return strrev($word);
}
}
$service = new Service();
echo $service->reverse('potato');
For an example, see:
https://3v4l.org/cKECo
Suggested Reading
http://wiki.c2.com/?ValueObject
https://en.wikipedia.org/wiki/Value_object
https://martinfowler.com/bliki/EvansClassification.html