[PHP] PHPdoc Enum types

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• Have you provided a full/minimal spec to reproduce the issue?
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Description

In the generated classes if an attribute is an enum, in its getter/setter, the phpdoc type is the class that contains the constants with the enum values instead of string:

enum class:

class Enum
{
    /**
     * Possible values of this enum
     */
    const FIRST = 'first';

    const SECOND = 'second';

Attribute setter(Enum type):

    /**
     * Sets type
     *
     * @param \Proj\Model\Enum|null $type type
     *
     * @return self
     */
    public function setType($type)
    {
        $this->container['type'] = $type;

        return $this;
    }

Here we set the property:

$obj->setType(Enum::FIRST);

As you can see the actual type passed is string and not Enum, so we will get a warning from the IDE.
So the phpdoc of the setter should be:

    /**
     * Sets type, see the accepted values in the Enum class
     *
     * @param string|null $type type
     *
     * @return self
     */
    public function setType($type)
    {
        $this->container['type'] = $type;

        return $this;
    }

openapi-generator version

5.4.0

No file or test is named in the issue. Start by locating the PHP generator's model and accessor template or entry point that produces enum property PHPDoc, then reproduce the example with a generated client. Done means enum-valued setters and getters document the passed value as string|null while retaining the enum class as the source of accepted constants.