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php – Access a static variable by $var::$reference

Posted by: admin April 23, 2020 Leave a comment

Questions:

I am trying to access a static variable within a class by using a variable class name. I’m aware that in order to access a function within the class, you use call_user_func():

class foo {
    function bar() { echo 'hi'; }
} 
$class = 'foo';
call_user_func(array($class, 'bar')); // prints hi

However, this does not work when trying to access a static variable within the class:

class foo {
    public static $bar = 'hi';
} 
$class = "foo";
call_user_func(array($class, 'bar')); // nothing
echo $foo::$bar; // invalid

How do I get at this variable? Is it even possible? I have a bad feeling this is only available in PHP 5.3 going forward and I’m running PHP 5.2.6.

How to&Answers:

You can use reflection to do this. Create a ReflectionClass object given the classname, and then use the getStaticPropertyValue method to get the static variable value.

class Demo
{
    public static $foo = 42;
}

$class = new ReflectionClass('Demo');
$value=$class->getStaticPropertyValue('foo');
var_dump($value);

Answer:

I think there is much better (more elegant) way then creating ReflectionClass instance. I also edited this code (and my answer) after few comments. I added example for protected variables (you can’t of course access them from outside the class, so I made static getter and call it using variable pattern as well). You can use it in few different ways:

class Demo
{
    public static $foo = 42;
    protected static $boo = 43;
    public static function getProtected($name) {
        return self::$$name;
    }
}

$var1 = 'foo';
$var2 = 'boo';
$class = 'Demo';
$func = 'getProtected';
var_dump(Demo::$$var1);
var_dump($class::$foo);
var_dump($class::$$var1);
//var_dump(Demo::$$var2); // Fatal error: Cannot access protected property Demo::$boo
var_dump(Demo::getProtected($var2));
var_dump($class::getProtected($var2));
var_dump($class::$func($var2));

Documentation is here:

http://php.net/manual/en/language.variables.variable.php

Answer:

For calling static members you can use a code like this:

call_user_func("MyClass::my_static_method");
// or
call_user_func(array("MyClass", "my_static_method"));

Unfortunately the only way to get static members from an object seems to be get_class_vars():

$vars = get_class_vars("MyClass");
$vars['my_static_attribute'];

Answer:

Have you try this?

class foo {
    static public $bar = "Hi";

    static public function bar() {
        echo "Hi";
    }
}

echo foo::$bar; // Output: Hi
foo::bar(); // Output: Hi

$class = "foo";
echo $class::$bar; // Output: Hi
$class::bar(); // Output: Hi
call_user_func($class, 'bar'); // Output: Hi