PHP Scope Issues? or is this expected? I don't understand why the `$this` in `Foo::bar()` is being treated as though it is referencing the `$bar` instance. If I declare `Foo::bar()` as static, then I get the expected error of `Using $this when not in object context.` How can you call a method from another object if `$this` in that object refers …

wtf.php

<?php

class Foo
{
	public function bar()
	{
		return $this->baz();
	}
	
	public function baz()
	{
		return 'buz';
	}
}

class Bar
{
	public function test()
	{
		return Foo::bar();
	}
}

$bar = new Bar;

echo $bar->test();
?>

Outputs the following:

PHP Fatal error:  Call to undefined method Bar::baz() in php shell code on line 1

🤦 I'm just stupid, that's the answer.

For the obvious one, you shouldn't be calling a non-static method statically.

What I don't get though is how the $this in Foo::bar is referencing the calling object.

This code just shouldn't work. You can't call an instance method $this->baz() if you don't have a Foo instance.

Some solutions

<?php

class Foo
{
    public static function bar()
    {
        return static::baz();
    }

    public static function baz()
    {
        return 'buz';
    }
}

class Bar
{
    public function test()
    {
        return Foo::bar();
    }
}

$bar = new Bar;

echo $bar->test();

and

<?php

class Foo
{
    public function bar()
    {
        return $this->baz();
    }

    public function baz()
    {
        return 'buz';
    }
}

class Bar
{
    public function test()
    {
        $f = new Foo;
        return $f->bar();
    }
}

$bar = new Bar;

echo $bar->test();

Or PHP 5.4

<?php

class Foo
{
    public function bar()
    {
        return $this->baz();
    }

    public function baz()
    {
        return 'buz';
    }
}

class Bar
{
    public function test()
    {
        return (new Foo)->bar();
    }
}

$bar = new Bar;

echo $bar->test();

I came across this scenario when debugging some old code, and couldn't figure out why I was getting the "Undefined method" error. No where that I could trace was calling the method in question. I stumbled upon the bug where the code followed this scenario where an instantiated class was calling another class method statically.

I ended up doing something similar to your second suggestion to fix it. I just thought it was very strange that $this within Foo::bar() was referencing the $bar instance.