According to PHP Standard Recommendations (PSR) –
1. Class names MUST be declared in StudlyCaps.
2. Class constants MUST be declared in all upper case with underscore separators.
3. Method names MUST be declared in camelCase.
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.