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PHP Variable Scope
The scope of a variable is the portion of the script in which the variable can be referenced.
PHP has four different variable scopes:
A variable declared within a PHP function is local and can only be accessed within that function. (the variable has local scope):
The script above will not produce any output because the echo statement refers to the local scope variable $a, which has not been assigned a value within this scope.
You can have local variables with the same name in different functions, because local variables are only recognized by the function in which they are declared.
Local variables are deleted as soon as the function is completed.
Global scope refers to any variable that is defined outside of any function.
Global variables can be accessed from any part of the script that is not inside a function.
To access a global variable from within a function, use the global keyword:
The script above will output 15.
PHP also stores all global variables in an array called $GLOBALS[index]. Its index is the name of the variable. This array is also accessible from within functions and can be used to update global variables directly.
The example above can be rewritten as this:
When a function is completed, all of its variables are normally deleted. However, sometimes you want a local variable to not be deleted.
To do this, use the static keyword when you first declare the variable:
static $rememberMe;Then, each time the function is called, that variable will still have the information it contained from the last time the function was called.