PHP: Calling class functions from within a class

Question

Starting a new PHP project and deciding that after a few years of PHP development, I'm thinking I should really start using PHP classes. I'm used to classes in the C++ world, so there's a few things I'm not quite sure about when porting this knowledge over to PHP.

In C++, you can automatically access any class variables without a prefix, in PHP, it appears that you need to prefix all such accesses (variables and function) with this->. I know what this is (or at least I think so, a pointer to the current class instance), but I'm not sure whether its required or preferred, or if there is any alternatives. My class will be using other functions within the same class (ie, itself) fairly heavily, so having to type this-> every time is going to get time consuming quite quickly.

The classes themselves are likely to be singletons, so I'm not sure whether to actually use a class, or just prefix the functions with an identifier.

Singletons in general are harmful, but in PHP there really isn't any benefit at all. I suggest you rework your design. This is not posted as an answer because it doesn't answer the question you asked. Good luck. — Levi Morrison
– Levi Morrison, Commented Dec 19, 2012 at 16:14
As Levi mentioned above, it sounds like your design might need a bit of reworking. Could you give a top level example of what one of your classes might look like? If you know that your classes are going to be self-referencing a lot, maybe there is quite a bit you can split out into other classes. — James
– James, Commented Dec 19, 2012 at 16:14
Get yourself a good IDE and you won't be worrying about typing $this becoming time consuming. You'll find it actually saves you time as it'll be able to autocomplete based on what properties are available. — RobMasters
– RobMasters, Commented Dec 19, 2012 at 16:17
I agree with the answers and comments presented here. I have decided against making some of the objects singletons and instead use dependency injection, as it seems a much more clean approach, and lends itself for more code re-usability and easier maintenance later. — squidge
– squidge, Commented Dec 20, 2012 at 13:43

DaveRandom · Accepted Answer · 2012-12-19 16:20:23Z

6

It is required that you reference the object to which the member belongs in order to access the member.

Every method call or property access is prefixed with $variable-> - $this is a magic variable that refers to the current object instance. Its use is not optional.

This is (amongst other reasons) because not every function in PHP is a method, there are also global functions. If you reference a function without associating it with an object, it is assumed to be a global function.

As a side note, you should avoid the use of singletons in PHP - there is no performance/memory gain to be found from using them because each concurrently executing script is garden-walled into its own memory space.

edited Dec 19, 2012 at 16:20

answered Dec 19, 2012 at 16:14

DaveRandom

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Comments

Tim Withers · Accepted Answer · 2012-12-19 16:16:44Z

2

The "pointer" (->) != C++ pointer.

$this means the current class and instance. All variables are accessed by using $this->variable; or $this->function();.

Static variables, and functions can be accessed using self::$variable or self::function()

Outside the class instance, you must indicate the class instance: $foo->variable; or $foo->function();

As far as I know, there is no way to access public/private/static/constant variables inside the class without using $this-> or self::

In reference to using an object of functions... up to you. Are you planning on expanding the code later to add more functions? Are all the functions somewhat related? If they are singleton functions, there is no harm in just writing a function instead of a class. It really just depends on what you are trying to accomplish.

answered Dec 19, 2012 at 16:16

Tim Withers

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2 Comments

Mike Mackintosh Over a year ago

You could always use ReflectionClass and its sibling Reflection* class's to access internal class items without $this. Wouldn't recommend it for this use, but it could be done.

Tim Withers Over a year ago

Very true, didn't think about that. But OPs point of the 7 characters ($this->) being too much to type repeatedly would probably mean using a function call to retrieve class variables would be too much as well.

Rawkode · Accepted Answer · 2012-12-19 16:18:23Z

0

Yes, you do have to use $this when accessing class method's or variables.

You need to remember that PHP doesn't require that variables be declared, so image the following situation:

<?
class A {
  public $a = 'Hello World!';
  function hello() {
    $a = 'hello';
    echo $a;
  }
}

$object = new A();
echo $object->hello();

$a would be local scope and $this->a would be the class variable.

answered Dec 19, 2012 at 16:18

Rawkode

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