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Catch use of $$this #4710
Description
Feature request
A colleague of mine caught a bug that used $$this->methodCall(). I know the phpstan/phpstan-strict-rules plugin can ban the use of $$, however I think PHPStan, out of the box, should prohibit $$this. Given $this always refers to an instance of a class, and not a string, it can't possibly be used as the lookup for something on the symbol table.
I played around with this in 3v4l.org, $$this just produces NULL, which PHPStan (0.12.81) does not pickup on to stop the method call. Consider the following code (available at https://3v4l.org/mhr52):
<?php
declare(strict_types=1);
final class Greeter
{
public function greet(): void
{
echo $$this->greetText();
}
public function greetText(): string
{
return 'Hello World';
}
}
$g = new Greeter();
$g->greet();You will get the following PHP error when trying to run:
Fatal error: Uncaught Error: Object of class Greeter could not be converted to string in /in/mhr52:9
However, PHPStan (with --level=max) will not report any issues.
Activity
ancarda commentedon Mar 17, 2021
After further experimentation, it seems this would work if you have
__toString, so perhaps PHPStan could check for that method's existence, and if it's not defined, reject$$this?ondrejmirtes commentedon Mar 17, 2021
Hi, this is very easy to implement.
$scope->getType($variable->name)when$variable->nameis Expr$type->toString()isErrorType, report the error.ancarda commentedon Mar 17, 2021
Thank you @ondrejmirtes! I'll give it a go tonight. I'd love to be able to finally contribute something to PHPStan!
ondrejmirtes commentedon Mar 20, 2021
There's also the opportunity to catch the same problem with
$foo->{$method}()etc.Updated PHPStan to commit f71b938503c3244953c1914d465c8a9a510242cc
phpstan-bot commentedon Sep 20, 2026
Closed via merging phpstan/phpstan-src#5871
github-actions commentedon Oct 22, 2026
This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.