Php global variable range analysis

Copy codeThe Code is as follows:
<? Php
$ A = 1;
Include 'B. inc ';
?>

The variable $ a will take effect in the included file B. inc. However, in user-defined functions, a local function range will be introduced. By default, any variable used in a function is limited to a local function.
Copy codeThe Code is as follows:
<? Php
$ A = 1;/* global scope */
Function Test ()
{
Echo $ a;/* reference to local scope variable */
}
Test ();
?>

This script does not have any output, because the echo statement references a local version of variable $ a and is not assigned a value within this range. You may notice that the global variables in PHP are a little different from those in C.
Global variables in PHP must be declared as global when used in functions)
Copy codeThe Code is as follows:
<? Php
$ A = 1;
$ B = 2;
Function Sum ()
{
Global $ a, $ B;
$ B = $ a + $ B;
}
Sum ();
Echo $ B;
?>

The output of the above script is "3 ".