php中static關鍵字的作用是什么

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

<?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
?>

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

<?php
static $name = 1;
$name++;
echo $name;
?>
另外：考慮到PHP變量作用域

<?php
include 'ChromePhp.php';
 
$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
?>