问题
PSR suggests, method names MUST be declared in camelCase and class names MUST be declared in StudlyCaps.
回答1:
StudlyCaps, also known as PascalCase, implies that the first capital of each subword is capitalized. camelCase implies, like a camel, that the humps are in the middle, therefore the first letter is not capitalized.
Compare Microsoft's standards for .NET.
Other well known capitalization styles are snake_case, where all words are concatenated in lowercase with underscores, and kebab-case, which is identical but uses a hyphen.
回答2:
CamelCase is where the first letter of each sub-word in a name is capitalised. The first letter of the whole name can be upper or lower case, and is generally (always?) lower case in programming.
StudlyCaps is a little weird. There are capital letters, but they can be at any letter according to some rule, not just the beginning of a sub-word. The classic example is (was) HoTMaiL.
My understanding of the PSRs is that their intention is that each sub-word should be capitalised in both instances, with classes having an initial upper-case letter and methods an initial lower-case letter.
回答3:
In PSR-12 there is an explanation of what they meant by StudlyCaps:
The term ‘StudlyCaps’ in PSR-1 MUST be interpreted as PascalCase where the first letter of each word is capitalized including the very first letter.
source: https://www.php-fig.org/psr/psr-12/#21-basic-coding-standard
P.S.
For clarity, there are two alternatives for camel case - upper camel case (initial uppercase letter, also known as Pascal case) and lower camel case (initial lowercase letter, also known as Dromedary case).
来源：https://stackoverflow.com/questions/32731717/what-is-the-difference-between-studlycaps-and-camelcase