使用PHP对象的'::'和' - >之间有什么区别？ [重复]

Question

This question already has an answer here:

• PHP Classes: when to use :: vs. ->? 7 answers

I'm a bit confused on the different conventions for objects and accessing their functions and variables.

I know how to use -> when I'm accessing something from an object, or within an object. I know the same when I'm in an object that I can use parent::item or classname::item but I don't know much beyond I use them because they work. Would someone break these down for me and explain when and why I should use one method vs the other?

class mammal{
    public age = 7;
}

class dog extends mammal{
    public dogSpecificVal;

    public function getAge(){
        return $this->age;
        return $parent::age;
        return $mammal::age;
    }
}

$clifford = new dog();
$cliffordAge = $clifford->getAge();

In that example, I used three different methods to retrieve the age. They all work, but I don't know why or when I should use one over the other.

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Answer 1

Within class methods non-static properties may be accessed by using -> (Object Operator): $this->property (where property is the name of the property). Static properties are accessed by using the :: (Double Colon): self::$property. See Static Keyword for more information on the difference between static and non-static properties.

http://php.net/manual/en/language.oop5.properties.php

http://php.net/manual/en/language.oop5.visibility.php