CODEWITHSUNDEEP
phpclassobjectscopeoperator-keyword
GullyBoy
GullyBoy

Reputation: 33

php.net manual not make sense of class Scope Resolution Operator ::

trying to learn php and caught on another snagg

Ok this is what they are saying on php.net below about the ::

The Scope Resolution Operator (also called Paamayim Nekudotayim) or in simpler terms, the double colon, is a token that allows access to static, constant, and overridden properties or methods of a class.

As of PHP 5.3.0, it's possible to reference the class using a variable. The variable's value can not be a keyword (e.g. self, parent and static).

When referencing these items from outside the class definition, use the name of the class. 

class MyClass {
    const CONST_VALUE = 'A constant value';
}

$classname = 'MyClass'; 

echo $classname::CONST_VALUE;  

echo MyClass::CONST_VALUE;
?>

now back to the above code

$classname = 'MyClass';

THAT IS A VARIABLE ! BEING GIVEN A 'STRING' VALUE OF 'MyClass'!

echo $classname::CONST_VALUE;

SO HOW IS THIS LINE EVEN POSSIBLE! IT HAS NOTHING TO DO WITH THAT CLASS!

THAT IS BASICALLY A SIMPLE VARIABLE WITH A STRING VARIABLE! SO HOW DOES IT MAGICALLY GET THE POWER TO ACCESS THAT CLASS CONSTANT WITH ::? ONLY THING SIMILAR I SEE IS THE STRING 'MyClass' buts in theory has no power to let that happen its just a string.

can someone explain because im having 100 snags a day im starting to think php was just made up as they went along its too many contradictory things in it.

Upvotes: 0

Views: 122

Answers (1)

xpuc7o
xpuc7o

Reputation: 333

In this case these two lines are basically the same. 

echo $classname::CONST_VALUE;  

echo MyClass::CONST_VALUE;

PHP tries to "cast" the string "MyClass" to a Class. If the class exists everything works like a charm.

Other example could be:

$instance = new $classname;

where $instance is a valid instance of MyClass.

In other words you can replace class name with its string representation.

Upvotes: 1

Related Questions