Composer Autoload does not autoload class [duplicate] - php

Question

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PHP class not found when using namespace
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Class not found in an simple PHP Script
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Closed 1 year ago.
I am following an tutorial on how to create a composer develop envoirement.
https://www.hostinger.com/tutorials/how-to-install-composer
I followed this but am getting the error 'Class "Timer" not found'.
Steps i took:
created a folder for the project
did the command "composer require phpunit/php-timer" on the folder. This automatically created the neccesary composer files.
created an php file called demo.php and copied the code from the tutorial (see code below)
Tried to run the php file with the command "php demo.php" and getting the error.
Code:
<?php
require __DIR__ . '/vendor/autoload.php';
Timer::start();
// your code
$time = Timer::stop();
var_dump($time);
print Timer::secondsToTimeString($time)

Answer 1

The classes in phpunit/php-timer are in a namespace called SebastianBergmann\Timer. Thus, you must either use the fully qualified class name:
\SebastianBergmann\Timer\Timer::start();
Or specify a use alias:
use SebastianBergmann\Timer\Timer;
Timer::start();
// ...
Time::stop();
I haven't looked in much detail but note that the docs for this package do not show static usage, so you might have to do:
use SebastianBergmann\Timer\Timer;
$timer = new Timer();
$timer->start();
// ...
$timer->stop();