Programming PHP

$counter = 10;
update_counter( );
echo $counter;
10
The $counter inside the function is local to that function, because we haven’t said
otherwise. The function increments its private $counter, whose value is thrown away
when the subroutine ends. The global $counter remains set at 10.
Only functions can provide local scope. Unlike in other languages, in PHP you can’t
create a variable whose scope is a loop, conditional branch, or other type of block.
Global scope
Variables declared outside a function are global. That is, they can be accessed from
any part of the program. However, by default, they are not available inside functions.
To allow a function to access a global variable, you can use the global keyword
inside the function to declare the variable within the function. Here’s how we
can rewrite the update_counter( ) function to allow it to access the global $counter
variable:
function update_counter ( ) {
global $counter;
$counter++;
}
$counter = 10;
update_counter( );
echo $counter;
11
A more cumbersome way to update the global variable is to use PHP’s $GLOBALS array
instead of accessing the variable directly:
function update_counter ( ) {
$GLOBALS[counter]++;
}
$counter = 10;
update_counter( );
echo $counter;
11
Static variables
A static variable retains its value between calls to a function but is visible only within
that function. You declare a variable static with the static keyword. For example:
function update_counter ( ) {
static $counter = 0;
$counter++;
echo "Static counter is now $counter\n";
}
$counter = 10;
32 | Chapter 2: Language Basics
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