PHP static static variable use method

Take a look at the following example:

 
<?php 
function Test() 
{ 
$w3sky = 0; 
echo $w3sky; 
$w3sky++; 
} 
?> 

This function sets the value of $w3sky to 0 and prints "0" each time it is called. Adding a variable to $w3sky++ does not work because the variable $w3sky does not exist once the function exits. To write a counting function that will not lose the count value, define the variable $w3sky as static:
As follows:

 
<?php 
function Test() 
{ 
static $w3sky = 0; 
echo $w3sky; 
$w3sky++; 
} 
?> 

This function prints the value of $w3sky and adds one for each call to Test().
Static variables also provide a way to handle recursive functions. A recursive function is a method that calls itself. Be careful when writing recursive functions, because they can go on forever without an exit. Make sure you have a way to stop the recursion. The following simple function recursively counts to 10, using the static variable $count to determine when to stop:
Examples of static variables and recursive functions:

 
<?PHP 
function Test() 
{ 
static $count = 0; 
$count++; 
echo $count; 
if ($count < 10) { 
Test(); 
} 
$count--; 
} 
?> 

Note: static variables can be declared as in the above example. Assigning the result of an expression to it in a declaration results in a parsing error.
Example of declaring static variables:

 
<?PHP 
function foo(){ 
static $int = 0;// correct 
static $int = 1+2; // wrong (as it is an expression) 
static $int = sqrt(121); // wrong (as it is an expression too) 
$int++; 
echo $int; 
} 
?>