Question

What strategies are available to creating accessors and mutators for a PHP class’ private members? Is this suggestion good: http://cormacscode.wordpress.com/2009/01/22/read-only-object-variables-in-php-using-magic-methods/

<?php
class classWithReadOnlyVar
{
    private $readOnlyVar;

    public function __get($varName)
    {
        return $this->$varName;
    }

    public function __set($varName,$varValue)
    {
    }
}

What if some members needed a private, public, or protected property method?

Answer 1

First of all, __get, __set, etc. are defined public and you cannot have them otherwise. Magic methods should be used wisely as it takes about three times as long to make a call to a magic method than simply calling a class method.

class A {
   public function __get($name) { ... }

   public function __getValue() { ... }     // <== is faster

}

Usually (normally, preferably), you will have your class members private or protected (never public) and have accessors and mutators to encapsulate them. Those accessors and mutator may be of any visibility, depending on what the user can do with the members. You may also have immutable classes by declaring only accessors for your members, which are initialized in the constructor only.

So, your sample class should read

class classWithReadOnlyVar {
   private $readOnlyVar;

   public function getReadonlyVar() {
     return $this->readOnlyVar;
   }

}

and should not use the magic methods.

There may be many reasons to avoid using magic methods at all :

1. they break code completion
2. they are slower at run-time
3. they make refactoring and maintenance a bit (lot) harder/complicated
4. you can’t have a protected magic method
5. etc.

---

Class members

Their visibility should be private or protected, it all depends if you want them accessible by inheritence. They should never be public as this breaks the OO paradigm.

Example of a protected member:

class A {
    protected $_name = 'A';

    public function getName() { return $this->_name; }
}

class B {
    protected $_name = 'B';   // getName() will not return 'B'
}

(without $_name being protected, this would not be possible, and no need to redefine the accessor)

Accessors

They should be protected or public. Having a private accessor makes no sense; a class should access it’s member directly. If the member needs processing, the class will know regardless when to call the accessor or not.

Mutators

They should be protected or public. As for the accessors, it makes no sense to have a private mutator… unless a very rare case when processing needs to be done internally. If a class member has no accessor, it should not have a mutator. It also makes no sense to have a mean to set a value without being able to get the value back somehow.