Change variable type phpDoc

Question

I have a base class that has several classes that inherit from it.

class Pet{
  ...
}
class Dog extends Pet{
   ...
}
class Cat extends Pet{
   ...
}

Then I have another class that consumes this class

class Person{
   /** @var Pet */
   public $pet;
}

These classes are based on some JSON object I will receive. The JSON object could contain a Dog object, or a Cat object. I run a switch statement to figure out which it is at runtime and handle it appropriately. However I would like to have type hinting via PHPDoc for whether it's a cat or dog. I have been unable to figure out how to specify at runtime that it's type has changed from a Pet to a Dog. This didn't work - it still just thinks it's a plain old Pet object.

$pet = json_decode($jsonObj);
if($pet->type == "dog"){
   /** @var Dog */
   $pet = $pet;
}

Any idea how to change the type to a sub-type at runtime with PHPDoc?

Sebastian Brosch · Accepted Answer · 2017-12-14 18:00:18Z

2

You can use the following using instanceof:

if ($pet instanceof Dog) {
    $dog = $pet;
    //now the IDE and runtime knows it is a Dog.
} elseif ($pet instanceof Cat) {
    $cat = $pet;
    //now the IDE and runtime knows it is a Cat.
}

Another way only using the DocBlock:

if ($pet->type === "dog") {

    /** @var Dog $dog */
    $dog = $pet;
    //now the IDE knows it is a Dog (at runtime this could be a Cat too).

} elseif ($pet->type === "cat") {

    /** @var Cat $cat */
    $cat = $pet;
    //now the IDE knows it is a Cat (at runtime this could be a Dog too).

}

edited Dec 14, 2017 at 18:00

answered Dec 14, 2017 at 17:54

Sebastian Brosch

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