PHP psr-0命名空间未找到类

Question

I get this error when doing a psr-0 namespace.

PHP Fatal error: Class 'myApp\\Db' not found in /Applications/MAMP/htdocs/elioop/User.php on line 7

Fatal error: Class 'myApp\\Db' not found in /Applications/MAMP/htdocs/elioop/User.php on line 7

I did a composer dump-autoload -o and still the error persists. The db and user files are within the directory, the root directory that is.

here is my current set up

composer.json

{
    "name": "poweruser/elioop",
    "require": {
        "phpunit/phpunit": "^7.4",
        "fzaninotto/faker": "^1.8"
    },
    "autoload":{
      "psr-0":{
        "myApp": ""
      }
    }
}

Db.php

<?php
namespace myApp;


class Db{

    private $db;

    public function connect()
    {

        try {
            $db = new PDO("mysql:host=127.0.0.1;dbname=eli9;port=8889", 'root', 'root');
            $db->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_WARNING);
                return $db;
        }
        catch (PDOException $e){
            echo $e->getMessage();
        }

    }


}

User.php

<?php

namespace myApp;

use myApp\Db;

class User extends Db{

    private $db;

    public function __construct()
    {

        $this->db = $this->connect();

    }

Index.php

<?php
session_start();
// Report simple running errors

require_once 'User.php';
$guest = new User();


$username = htmlentities(trim($_POST['txt_username']));
$unpass = htmlentities(trim($_POST['txt_password']));
$password = password_hash($unpass, PASSWORD_BCRYPT, ['cost' => 12] );
$unemail = $_POST['txt_email'];
$email = filter_var($unemail, FILTER_VALIDATE_EMAIL);
......

Answer 1

Why PSR-0 and not PSR-4 ?

Also, you don't seem to be using the composer PSR-0 autoloader. You should do:

<?php
require_once 'vendor/autoload.php'; //Composer autoloader


session_start();
// Report simple running errors


$guest = new \myApp\User();

Once you've loaded the composer autoloader then all your composer autoloading configuration should take effect.