What are static variables? What are its characteristics? Where is the scope? (with examples)

The previous article introduced you to "How to define global variables in PHP? How to declare? what is the function? (Summary) 》, this article continues to introduce to you what are static variables? What are its characteristics? Where is the scope? (With examples), this article comes with examples, why don’t you come in and take a look! ! !

What is a static variable:

A variable declared using static inside a function is a static variable;

Characteristics of static variables:

• Static variables will only be initialized once;

• Static variables will be initialized after the function ends It will not be recovered later;

• Static functions are generally used to count the number of function calls;

<?php
     /****** 静态函数*/
     function addNum(){
      $a = 1;
       echo $a. &#39;<br/>&#39;;
       $a ++;
     }
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();

?>

Code analysis:

First we use function to define a function [addNum()], then assign the initial value ($a), output (echo) $a, and then let $a increment;

If we start calling addNum(); what is the result we output at this time? According to the results of the code operation below, we can see that they are all 1; because we call the function, it will be executed immediately after the function is called. When the function is executed, enter the function, and then the variables will be declared and executed. When the execution is completed , the variable will be released accordingly, and by analogy, the results we get are all 1; the above makes us ordinary variables, and what we define is a static function because there is a static variable inside the function;

The running results are as follows:

##About static variables

<?php
     /****** 静态函数*/
     function addNum(){
       static $a = 1;
       echo $a. &#39;<br/>&#39;;
       $a ++;
     }
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();
     addNum();

?>

Code analysis:

First we declare a static variable (static $a), and then execute the code. The result of the operation is 1,2,3,4,5,6,7;

As shown in the figure below ;

In the static variable, when we first called and executed this variable inside the function, we declared the static variable and initialized it to 1, and this time

The call is only executed once;Static variables generally we will count the number of function calls;

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