I stopped at online test question. They ask for experts but instead of asking for real-life solutions, you need to find correct "echo" result on mess of characters, numbers, constants... Something that no sane person would ever write and is completely irrelevant. It was basically an insult to answer things like that. I write code with 100% pass on phpstan (max level), deep understanding of Symfony (even undocumented features), been using nested-set for 9 years... and yes, I don't know the answers to those questions as it makes no sense to even try reading that mess. Few weeks later, I got email asking me why I quit my test. After few messages with guy from Serbia, I figured the problem; they don't have actual programmers with real-life experience but only people who finished university and have bare minimum of knowledge. Suggestion: if you are looking for experts, make the first question something like this: foreach($this->getResults() as $result) {....} function getResults() { return range(1, 100000000); } Task: refactor "getResults()" function to not eat all the memory. Answer: generators. Make that to be the easiest question. And it actually is, pretty much same example from php.net. Bonus: allow start and end values of that range. That's how you find quality programmers.