Initialize a class property - php

Question

Is there a way to initialize a PHP class property from another class property? I have a series of properties I'd like to depend upon each other for easy modification of the root value:
class Anon {
private static $a = 5;
private static $b = '+' . (2 * self::$a);
}
However, this causes a syntax error. I've had trouble searching for this, but I haven't seen anybody trying to do this!

Answer 1

You can initialise the static variable by using an Init method
<?php
class Anon {
private static $a = 5;
private static $b ;
public static function Init(){
self::$b = '+' . (2 * self::$a);
}
public static function getB(){
return self::$b;
}
}
Anon::Init();
echo Anon::getB();
?>

Answer 2

Depends on how you're using the class, but maybe this will help:
class Anon {
private static $a = 5;
private static $b;
function __construct() {
self::$b = '+' . (2 * self::$a);
}
public function getB() {
return self::$b;
}
}
$anon = new Anon;
echo $anon->getB();

Answer 3

Unfortunately PHP can not parse non-trivial expression while class is being loaded
Here is a solution to initialize your static members
class Anon {
private static $a;
private static $b;
public static function init () {
self::$a = 5;
self::$b = '+' . (2 * self::$a);
}
}
Anon::init();

Answer 4

You can't access private class properties directly. You can with public though.
class Anon {
public static $a = 5;
}
print Anon::$a;
or use a public function like the other examples to access $b;
class Anon {
private static $a = 5;
private static $b;
public static function init() {
return self::$b = '+' . (2 * self::$a);
}
}
echo Anon::init();