What is the function of static keyword in php

The functions of the static keyword in php are: 1. Put it inside the function to modify the variable, and the variable value will still be saved after the function is executed; 2. Put it in the class to modify the attributes or methods. If the modification is of a class attribute, the value is retained; 3. Modify the variable in the method of the class; 4. Modify the variable in the global scope.

The functions of the static keyword are as follows:

1. Put it inside the function to modify the variable;

2. Put it in the class to modify the attributes or methods;

3. Put it in the class method to modify the variables;

4. Modify variables in the global scope; the different meanings represented by the

keywords are as follows:

1. After the function is executed, the variable value is still saved

As shown below:

<?php
function testStatic() {
    static $val = 1;
    echo $val;
    $val++;
}
testStatic();   //output 1
testStatic();   //output 2
testStatic();   //output 3
?>

2. Modified attributes or methods can be accessed through the class name. If the modified attribute is a class attribute, the reserved value

is as follows:

<?php
class Person {
    static $id = 0;
 
    function __construct() {
        self::$id++;
    }
 
    static function getId() {
        return self::$id;
    }
}
echo Person::$id;   //output 0
echo "<br/>";
 
$p1=new Person();
$p2=new Person();
$p3=new Person();
 
echo Person::$id;   //output 3
?>

3. The variables in the method of modifying the class

are as follows:

<?php
class Person {
    static function tellAge() {
        static $age = 0;
        $age++;
        echo "The age is: $age
";
    }
}
echo Person::tellAge(); //output &#39;The age is: 1&#39;
echo Person::tellAge(); //output &#39;The age is: 2&#39;
echo Person::tellAge(); //output &#39;The age is: 3&#39;
echo Person::tellAge(); //output &#39;The age is: 4&#39;
?>

4. The variables that modify the global scope have no practical meaning

are as follows: Display:

<?php
static $name = 1;
$name++;
echo $name;
?>
另外：考虑到PHP变量作用域

<?php
include &#39;ChromePhp.php&#39;;
 
$age=0;
$age++;
 
function test1() {
    static $age = 100;
    $age++;
    ChromePhp::log($age);  //output 101
}
 
function test2() {
    static $age = 1000;
    $age++;
    ChromePhp::log($age); //output 1001
}
 
test1();
test2();
ChromePhp::log($age); //outpuut 1
?>

It can be seen that these three variables do not affect each other. In addition, there are only global scope and function scope in PHP, not block scope.

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