How to know if static property is inherited in php?

Question

I have a $class_name = 'B';

And :

class A
{
    static $foo = 42;
    static $baz = 4;
}

class B extends A
{
   static $bar = 2;
   static $baz = 44;
}

How can I know if $class_name::$foo is a static property for the $class_name or if it's a inherited static property?

I need following result :

$class_name = 'A';
isOwnStaticProperty($class_name, 'foo'); //TRUE : is a static property of this class

$class_name = 'B';
isOwnStaticProperty($class_name, 'foo'); //FALSE : is NOT a static property of this class

$class_name = 'B';
isOwnStaticProperty($class_name, 'bar'); //TRUE : is a static property of this class

$class_name = 'A';
isOwnStaticProperty($class_name, 'bar'); //FALSE : is NOT a static property of this class

$class_name = 'B';
isOwnStaticProperty($class_name, 'baz'); //TRUE : is a static property of this class

$class_name = 'A';
isOwnStaticProperty($class_name, 'baz'); //TRUE : is a static property of this class

How implement isOwnStaticProperty() function?

Answer 1

You can use the ReflectionClass with the method getProperties to retrieves the reflected properties. To filter you can use ReflectionProperty

<?php

class A
{
    static $foo = 42;
    static $baz = 4;
}

class B extends A
{
   static $bar = 2;
   static $baz = 44;
}

function isOwnStaticProperty($class, $prop) {
    $reflect = new ReflectionClass($class);
    //Filtering only the statics values with ReflectionProperty::IS_STATIC
    $props   = $reflect->getProperties(ReflectionProperty::IS_STATIC);
    foreach ($props as $object) {
        if($object->class == $class && $object->name == $prop) {
            return true;
        }    
    }
    return false;
}   


$class_name = 'A';
echo isOwnStaticProperty($class_name, 'foo') ? "TRUE<br>\n" : "FALSE<br>\n"; 

$class_name = 'B';
echo isOwnStaticProperty($class_name, 'foo') ? "TRUE<br>\n" : "FALSE<br>\n"; 

$class_name = 'B';
echo isOwnStaticProperty($class_name, 'bar') ? "TRUE<br>\n" : "FALSE<br>\n"; 

$class_name = 'A';
echo isOwnStaticProperty($class_name, 'bar') ? "TRUE<br>\n" : "FALSE<br>\n"; 

$class_name = 'B';
echo isOwnStaticProperty($class_name, 'baz') ? "TRUE<br>\n" : "FALSE<br>\n"; 

$class_name = 'A';
echo isOwnStaticProperty($class_name, 'baz') ? "TRUE<br>\n" : "FALSE<br>\n"; 

OUTPUT:

TRUE
FALSE
TRUE
FALSE
TRUE
TRUE

Answer 2

Edit: This answer is valid only for revision #1 of the question, when the parent class contains no property by the same name.

Use get_parent_class in combination with isset and variable variables:

function isOwnStaticProperty($class, $property)
{
    $parent = get_parent_class($class);
    return isset($class::$$property) && ($parent === FALSE || !isset($parent::$$property));
}

This checks whether $class has a static property named $property, and either has no parent class, or the parent class does not have such a property.

Note the two $ before property in isOwnStaticProperty.

Call it like

echo isOwnStaticProperty('A', 'foo'); // TRUE
echo isOwnStaticProperty('A', 'bar'); // FALSE
echo isOwnStaticProperty('B', 'foo'); // FALSE
echo isOwnStaticProperty('B', 'bar'); // TRUE