PHP Static Variables: Why Doesn't It Reset?

[topsquark]

The code

<?php
function myTest() {
static $x = 0;
echo $x;
$x++;
}

myTest();
echo "<br>";
myTest();
echo "<br>";
myTest();
?>

is supposed to generate
0
1
2

My question is this: If we declare $x = 0 in the function then why doesn't it reset to 0 every time we run the function?

-Dan

 

[MarkFL]

Hey Dan,

A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope. [m]$x[/m] is initialized only in the first call of the function and every time the myTest() function is called, it will print the value of [m]$x[/m] and increment it. :)

 

[topsquark]

Hey Dan,

A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope. [m]$x[/m] is initialized only in the first call of the function and every time the myTest() function is called, it will print the value of [m]$x[/m] and increment it. :)

Thank you. But couldn't we do the same thing by declaring $x as a global variable?

-Dan

 

[MarkFL]

Thank you. But couldn't we do the same thing by declaring $x as a global variable?

-Dan

Yes, you could write:

function increment_x()
{
	global $x;
	echo $x;
	$x++;
}

$x = 0;
increment_x();
echo "<br>";
increment_x();
echo "<br>";
increment_x();

 

[topsquark]

Ah good! That means I am actually learning something! (Dance)

-Dan

 

[I like Serena]

For the record, a static and a global variable are the same thing as far as life time is concerned (called static duration).
The difference is that a static variable has limited visibility - it can only be accessed within the scope in which it has been defined (that is, up to the enclosing '}').