Naming Styles Definition

When writing code, programmers often adopt a naming convention for terms used in their code.

In particular, the following styles exist:

First-lower CamelCase

This convention is used in languages such as Java and PHP for class methods.

$x = new userGroup();
$a->newSession();
openFileAndParse($filename, stripWhitespace);
writeToDisk($fd);

First-upper CamelCase Convention

This convention is used for class names in Java and PHP, and sometimes object methods.

$x = new UserGroup();
$a->NewSession();
OpenFileAndParse($filename, StripWhitespace);
WriteToDisk($fd);

Lower Underscored

This convention separates distinct words by an underscore.

$x = new user_group();
$a->new_session();
open_file_and_parse($filename, strip_whitespace);
write_to_disk();

Upper Underscored

This convention is usually used for constants in many languages.

$X = NEW USER_GROUP();
$A->NEW_SESSION();
OPEN_FILE_AND_PARSE($FILENAME, STRIP_WHITESPACE);
WRITE_TO_DISK($FD);

It's rarely used for methods or functions, although in PHP it could be as methods and functions in PHP are case-insensitive.