PHP & Case Sensitivity
In PHP, variable and constant names are case sensitive, while function names are not.
As far as I am aware, PHP is the only language in which this happens. All other languages I have used are either totally case sensitive or totally case insensitive.
Why is PHP partially case senstive?
Please note, that I am not asking which names are case sensitive, but why.
Update
I thought I might add, for the benefit of those who think I am asking which, the following list:
Case Sensitive
- Strings
- Variables
- Object Properties
- Constants, by default
Case Insensitive
- Key Words etc
- Functions
- Object Methods
- Constants, if defined accordingly
- Class Names
Note:
- Classes are thus a mixed bag:
- The
classkeyword is case insensitive - Class names are case insensitive, for declaration, instantiation, and static calls
- Class methods, being functions, are case insensitive
- Class properties, being variables & constants, are case sensitive
- The
- Because Strings are case sensitive, anything that relies on strings, such as array keys and values, is also case sensitive
Answer
FYI
Case sensitive (both user-defined and PHP defined)
- variables
- constants
- array keys
- class properties
- class constants
Case insensitive (both user defined and PHP defined)
- functions
- class constructors
- class methods
- keywords and constructs (if, else, null, foreach, echo etc.)
In php.net
Basics
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.
Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscores, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'
Some useful Links