Question

I’m trying to find a workaround for static variables not being copied over to extending classes (which doesn’t play nicely with late static binding), here is what I thought might work, but gives me a “PHP Fatal error: Can’t use function return value in write context” :

<?php

class Person
{
    protected static $tlsb_names = ['name'];
    protected static $tlsb_vars  = [];

    public static function & __callStatic($method,$args)
    {
        echo "call static " . $method . " on " . get_called_class() . "\n";
        if(in_array($method,static::$tlsb_names))
        {
            if(!array_key_exists(get_called_class(),static::$tlsb_vars))
            {
                static::$tlsb_vars[get_called_class()] = [];
            }
            if(!array_key_exists($method, static::$tlsb_vars[get_called_class()]))
            {
                echo "set var $method for " . get_called_class() . "\n";
                static::$tlsb_vars[get_called_class()] = null;
            }
            return static::$tlsb_vars[get_called_class()][$method];
        }
    }

    public static function show_name()
    {
        static::name() . "\n";
    }

    public static function call_me_al()
    {
        static::name() = "Al";
    }

    public static function call_me_joe()
    {
        static::name() = "Joe";
    }   
}

class Al extends Person{}
class Joe extends Person{}

Al::call_me_al();
Joe::call_me_joe();

Al::show_name();
Joe::show_name();

The problematic part is with the lines :

public static function call_me_al()
{
    static::name() = "Al";
}

Apparently this is a compile-time error since non of my echo’s are run.

What am I doing wrong here?

Answer 1

The following line of code is wrong:

public static function & __callStatic($method,$args)

You need to match the definition of that __callStatic function^Docs and that is without return by reference:

public static function __callStatic($name, $arguments)

So what you try to achieve is not possible.

And the other problem you circle around with should be able to solve with late static binding (LSB)^Docs.

Also keep in mind that Magic is hard to debug, so get your step-debugger ready and step through the application so you can better understand what is actually happen. The debugger in PHP is called Xdebug, most PHP IDEs and editors support it.