NYCPHP Meetup

[David Krings]

Shadab Wadiwala wrote:
> Hi, community !!
> 
> 
> Can somebody make me understand what is the difference between the 
> CONSTANT and the GLOBAL VARIABLE ??
> 

A constant is a value that never changes, whereas a variable can change 
its value (which means that there cannot be something like a "constant 
variable" or a "variable constant", similar to a "variable datum", which 
is also an oxymoron).
A global variable is one that is available in any context (any script 
and any function even when not explicitly declared in that one).

Examples: the constant M_PI has the value of pi. No matter what you do, 
M_PI does not change its value. You can also use the function pi() to 
have the value of M_PI returned.

You can use the PHP keyword global to make any variable to have global 
scope. Some variables are global per definition and are called the 
superglobals, such as $_SERVER or $_SESSION.

Hope that helps,

	David