How to get the Class property set in another class in PHP

Question

I have created two classes User and Post. In the Post class I have created a method getPostUser that should return the User object for the passed postId. With my code, it is setting all property but when I am trying to get the value either from the Post or User object it is giving me the following error.

Fatal error: Uncaught Error: Typed property App\User\User::$phone must not be accessed before initialization in ...\www\learnphp\src\User\User.php:72 Stack trace: #0 ...\www\learnphp\index.php(18): App\User\User->getPhone() #1 {main} hrown in ...\www\learnphp\src\User\User.php on line 72

What I want to know is

Is the way I am writing code correct or wrong?
How to get the entire User object by passing postId?
Is there any better way to write such code?

User Class

<?php

namespace App\User;


class User
{

    /**
     * @var int
     */
    private int    $userId;

    /**
     * @var string
     */
    private string $userName;

    /**
     * @var string
     */
    public string $email;

    /**
     * @var int
     */
    public int $phone;

    /**
     * User constructor.
     *
     * @param int    $userId
     * @param string $userName
     */
    public function __construct(int $userId, string $userName)
    {
        $this->userId   = $userId;
        $this->userName = $userName;
    }

    /**
     * @return string
     */
    public function getEmail()
    : string
    {
        return $this->email;
    }

    /**
     * @param string $email
     */
    public function setEmail(string $email)
    : void {
        $this->email = $email;
    }

    /**
     * @return int
     */
    public function getPhone()
    : int
    {
        return $this->phone;
    }

    /**
     * @param int $phone
     */
    public function setPhone(int $phone)
    : void {
        $this->phone = $phone;
    }


    /**
     * @return int
     */
    public function getUserId()
    : int
    {
        return $this->userId;
    }

    /**
     * @param int $userId
     */
    public function setUserId(int $userId)
    : void {
        $this->userId = $userId;
    }

    /**
     * @return string
     */
    public function getUserName()
    : string
    {
        return $this->userName;
    }

    /**
     * @param string $userName
     */
    public function setUserName(string $userName)
    : void {
        $this->userName = $userName;
    }


}

Post Class

<?php

namespace App\Post;


use App\User\User;

class Post
{
    /**
     * @var int
     */
    private int $postId;

    /**
     * @var int
     */
    private int $userId;

    /**
     * @var string
     */
    private string $userName;

    /**
     * @var string
     */
    private string $content;

    /**
     * @param string         $content
     * @param \App\User\User $user
     *
     * @return \App\Post\Post
     */
    public function createPost(string $content, User $user)
    : Post {

        $this->content  = $content;
        $this->userId   = $user->getUserId();
        $this->userName = $user->getUserName();

        $this->postId = 10; //db generated postId

        return $this;
    }

    /**
     * @param int $postId
     *
     * @return \App\User\User
     */
    public function getPostUser(int $postId)
    : User {

        if ($this->postId == $postId) {
            $user = new User($this->userId, Post::class);
            $user->setEmail('johndoe@email.com');
            $user->setPhone(457845412);

            return $user;
        }

        return NULL;

    }

    /**
     * @return int
     */
    public function getPostId()
    : int
    {
        return $this->postId;
    }

    /**
     * @param int $postId
     */
    public function setPostId(int $postId)
    : void {
        $this->postId = $postId;
    }

    /**
     * @return int
     */
    public function getUserId()
    : int
    {
        return $this->userId;
    }

    /**
     * @param int $userId
     */
    public function setUserId(int $userId)
    : void {
        $this->userId = $userId;
    }

    /**
     * @return string
     */
    public function getContent()
    : string
    {
        return $this->content;
    }

    /**
     * @param string $content
     */
    public function setContent(string $content)
    : void {
        $this->content = $content;
    }

    /**
     * @return string
     */
    public function getUserName()
    : string
    {
        return $this->userName;
    }

    /**
     * @param string $userName
     */
    public function setUserName(string $userName)
    : void {
        $this->userName = $userName;
    }


}

Index File

<?php

use App\Post\Post;
use App\User\User;

require "vendor/autoload.php";

$user = new User(7, 'johndoe');
$post = new Post();

echo '<pre>', print_r($post->createPost('This is the hello world post.', $user), TRUE);
echo $post->getPostId(), '<br>';
echo $post->getContent(), '<br>';
echo $post->getUserName(), '<br>';
echo $post->getUserId(), '<br>';


var_dump($post->getPostUser(10));

echo $user->getPhone();

`public int $phone;` tells the PHP interpreter that `$phone` is going to be an `int`. What you are doing is a [lazy initialization](https://wiki.php.net/rfc/typed-properties) and PHP doesn't like it. You can set the phone number to some dummy value I presume in the constructor, however this isn't a good idea. You better have phone number passed in the constructor for proper object properties initialization. — nice_dev, Dec 17 '19 at 12:18
@vivek_23 thanks for the details. How I can get the value for instance `Phone` in this case from the `Post` object method `getPostUser` as this is returning `User` object or there is no way to get the Phone number from the `Post` object and must have to use `User` object? — Code Lover, Dec 17 '19 at 12:37
@CodeLover You would have to do `$post->getPostUser(10)->getPhone()` to get the phone number. Ideally, you should have an instance variable inside Post class which holds the user object through the lifecycle of post object. — nice_dev, Dec 17 '19 at 12:47
For future reference: https://meta.stackoverflow.com/questions/333952/why-should-i-provide-a-minimal-reproducible-example-for-a-very-simple-sql-query — Strawberry, Dec 18 '19 at 10:12

Daniel · Answer 1 · 2019-12-17T12:36:08.857

The error you are getting is because your $phone variable in the User class has been declared but not initiated. When you call getPhone on the User object, its phone number has no value:

$user = new User(7, 'johndoe');
$post = new Post();

echo '<pre>', print_r($post->createPost('This is the hello world post.', $user), TRUE);
echo $post->getPostId(), '<br>';
echo $post->getContent(), '<br>';
echo $post->getUserName(), '<br>';
echo $post->getUserId(), '<br>';

var_dump($post->getPostUser(10));

echo $user->getPhone(); // phone attribute has not been set

You could either initiate it in the constructor or directly inline with declaration with a default value

public int $phone = 0

As mentioned in the comments above, you should probably define a constructor for the User class with phone as a mandatory parameter if all users must have a phone number.

Concerning your will to retrieve a user by ID, the only viable way in a real application would be to set up a SQL repository and fetch the user by post ID using SQL queries (or an ORM if you are using one)

How to get the Class property set in another class in PHP

User Class

Post Class

Index File

1 Answers1