static class scope 在 Z2FEC392304A5C23AC138DA22847F9B7C 是否有任何变化

Question

Today I saw a new type of code execution in PHP that was slightly different from the previous versions. The following code is executed as follows from version 8.1 onward. Anyone have an idea why?

<?php

class test {

    /**
     * A test static variable in class
     * @var int $var
     */
    private static int $var;

    /**
     * A method to set value in private variable with name $var
     * @param int $var
     */
    public static function setVar(int $var): void
    {
        self::$var = $var;
    }

    public static function getVar()
    {
        $vars = get_class_vars(__CLASS__);
        echo '<pre>' . print_r($vars, 1) . '</pre>';
    }

}

test::setVar(2);
test::getVar();
test::setVar(3);
test::getVar();

Run result in PHP 8.0.11

Array
(
    [var] => 2
)

Array
(
    [var] => 3
)

Run result in PHP 8.1.6

Array
(
    [var] => 
)

Array
(
    [var] => 
)

Answer 1

The change is not to static properties themselves, but to the get_class_vars function. The documented purpose of that function has always been to return the default values of all properties, so returning the current value for static properties in previous versions was technically a bug.

To get the current values of static properties, you can instead use the method ReflectionClass::getStaticProperties , eg

class Test {
    public static $var = 0;
}

echo "Before:-\n";
echo "Default: "; var_dump( get_class_vars(Test::class) );
echo "Current: "; var_dump( (new ReflectionClass(Test::class))->getStaticProperties() );

test::$var = 42;

echo "After:-\n";
echo "Default: "; var_dump( get_class_vars(Test::class) );
echo "Current: "; var_dump( (new ReflectionClass(Test::class))->getStaticProperties() );

Running this across lots of PHP versions shows that for PHP versions back to 5.5 (and probably beyond, if the syntax of the example is tweaked) the output is (incorrectly):

Before:-
Default: array(1) {
  ["var"]=>
  int(0)
}
Current: array(1) {
  ["var"]=>
  int(0)
}
After:-
Default: array(1) {
  ["var"]=>
  int(42)
}
Current: array(1) {
  ["var"]=>
  int(42)
}

For PHP 8.1, it is (correctly):

Before:-
Default: array(1) {
  ["var"]=>
  int(0)
}
Current: array(1) {
  ["var"]=>
  int(0)
}
After:-
Default: array(1) {
  ["var"]=>
  int(0)
}
Current: array(1) {
  ["var"]=>
  int(42)
}