Educator

Variable Scope

• Variable scope refers to the part of a script where a variable can be accessed.
• Variables defined in a script outside of a function have global scope . A variable with global scope can be used anywhere within the script it is defined or the files included in the script it is defined (*except within functions).
• Variables defined in functions, including function parameters, have what is known as local function scope . Variables with local function scope can only be accessed from within the function.
• The global keyword allows variables with global scope to be used within functions and variables with local function scope to be used in the global scope.
• Superglobal variables are pre-defined associative array variables that are always available in both the global scope and local function scope.
• The $GLOBALS superglobal contains all of the variables currently in the global scope of a script. It can be used to access global variables from within local function scope.
• All constants are accessible in both the global and local function scope.
• Functions have global scope, meaning as long as a function is defined within a script or one of its include files, it can be called anywhere within that script or its include files.
• Additional Resources:
  • PHP Manual - Variable Scope
  • PHP Manual - Superglobals
  • PHP Manual - $GLOBALS Superglobal