Without sounding too pretentious, I think naming things well is a skill that comes with experience. As a software designer you are given the complete freedom to name your variables, functions and classes however you choose, within the constraints of the language.

Here are some tips from lessons I've learned:

• be clear - give things their proper name. Name things how you would talk about them with the domain experts and users. Don't give variables or methods one letter names. The only exceptions may be when in a very arithmetic heavy calculations, for example, substituting $w and $h for $width and $height may be okay.
• be specific where necessary - I used to work on a system where every collection or array was called $data. If you have a collection of Person items, please don't name it $array or $data, what's wrong with $people?!
• be abstract where necessary - if you're naming an abstract class or interface, try to be generic, give it the abstract name you might use when talking about it in conversation.
• question existing names and conventions - how does it sound when you read the method? Does it flow? Could you speak it in conversation?
• use conventions - in PHP methods and properties are written in camelCase(). Classes and Namespaces should use StudlyCase. If in doubt, the PSR2 standards is a good starting place.
• be consistent - if a method is command, it should sound like a command, e.g. sendEmail(). If a method is interrogative, it will probably be prefixed with get*, find*, is*, or has*. get* implies a retrieval of something normally instantiated on an object, like a property. find* implies that some computation or searching may be necessary in order to retrieve something. is* and has* both imply a boolean true/false return type so they may be used in conditionals, for example if ($object->isValid()) {...} and if ($post->hasComments()) {...}.
• be unambiguous - $list->empty() - does this imply a question to see if a list is empty, or a command to empty the list?
• don't needlessly repeat types - for example $basket->addToBasket($product) would be better as $basket->add($product).
• comments are code smells I find if I need to comment something it's because my code is so complicated I can't follow it or remember how it's working. This is a definite code smell, but one that is easy to fix by either extracting a complicated logic into a method or variable and using the old comment as a method or variable name.
• Don't be afraid to rename things - it is super easy to rename things especially with an IDE like phpStorm. If something doesn't sound quite right or if something changes you are free to change method/variable/class names to reflect that change.

Do you have any other naming tips or things that you hate seeing in other code bases? Please share in the comments below and I'll update my list!