Detailed explanation of how to use static variables in php

Detailed explanation of how to use static variables in php_PHP tutorial

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Release： 2016-07-21 15:37:13

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Take a look at the following example:

Copy code The code is as follows:

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

Every time this function is called Set the value of $w3sky to 0 and output "0". Increasing the variable $w3sky++ by one has no effect, because the variable $w3sky does not exist once this function exits. To write a counting function that will not lose this count value, define the variable $w3sky as static:
as follows:

Copy code The code is as follows:

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

Every time this function calls Test(), it will output the value of $w3sky and increment it by one.
Static variables also provide a way to deal with recursive functions. A recursive function is a method that calls itself. Be careful when writing recursive functions, as they may recurse indefinitely without an exit. Be sure to have a way to abort the recursion. The following simple function recursively counts to 10, using the static variable $count to determine when to stop:
Example of static variables and recursive functions:

Copy code The code is as follows:

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

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

Copy code The code is as follows:

 
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; 
} 
?> 