PHP Static Class Properties

[peridian]

Hello,

I should have made a note of which version of php 5 I am currently using, but I didn't (I'm pretty sure it's 5.2.2).

Ayway, I just want to clarify that my understanding of the static keyword under php is correct, as I tried something earlier that I would have expected to work in any other OOP language, and it didn't.

Am I correct in stating:

a) Static class properties cannot be assigned values after declaration.
b) Static variables cannot be assigned an object data type, only primitives.
c) Static class properties cannot be accessed by an instantiated object through the $this notation.

I tried implementing something similar to the code below, which I would have expected to work, but it seems php handles static slightly differently to other languages.

Regards,
Rob.

class A
{
  //Various instance variables and methods.
}
 
class B
{
  //Did not have a problem with either of the below lines.
  protected static var;
  protected static flag = false;
  //Did have a problem with this though:
  //protected static var = new A;
 
  public function __construct()
  {
    if(!self::flag) {
      //Had a problem with both the following lines.
      self::var = new A;
      self::flag = true;
    }
  }
}
 
class C extends B
{
  public function __construct()
  {
    parent::__construct();
  }
}
 

[pbmods]

Heya, Peridian.

Only point 3 is correct; you don't use $this to access static properties:

class Tester
{
    protected static $myVar;
 
    public static function getVar($val)
    {
        return self::$myVar;
    }
 
    public static function setVar($val)
    {
        return self::$myVar = $val;
    }
}
 
class Outputter
{
    public function __tostring()
    {
        return 'Outputter';
    }
}
 
Tester::setVar('Hello, World!');
echo Tester::getVar();    // 'Hello, World!'
 
Tester::setVar(new Outputter());
echo Tester::getVar();    // 'Outputter'
 

[peridian]

Ahh, awesome. I can't believe it but when I checked my syntax in the code, I had dropped the $ from after the :: part. I think I must have thought I was using a static method call or something.

EDIT: Doh, don't worry, just answered my own question. Thanks a lot.