Demo php clase name collision problems

a.php

<?php

echo "Running test from: " . PHP_VERSION . PHP_EOL;

// Comment this line to trigger other errors
require_once __DIR__ . '/unconditional.php';

require_once __DIR__ . '/b.php';
require_once __DIR__ . '/c.php';

$a = new Already_Defined();

// Uncommenting the top require_once would cause an error here
require_once __DIR__ . '/unconditional.php';

try {
    // Uncommenting this line would cause fatal errors
    // class Already_Defined {};

    // Uncommenting the top require_once would cause an error here
    require_once __DIR__ . '/unconditional.php';
} catch ( Error $e ) {
    echo "Creating the class unconditionally would error." . PHP_EOL;
    var_dump($e);
}

echo "Ran to completion, created class instance: " . get_class($a) . PHP_EOL;

b.php

<?php

if (class_exists('Already_Defined') ) {
    return;
}

class Already_Defined {
    public function __construct() {
        echo 'Initialized from ' . __FILE__ . PHP_EOL;
    }
}

c.php

<?php

if (class_exists('Already_Defined') ) {
    return;
}

class Already_Defined {
    public function __construct() {
        echo 'Initialized from ' . __FILE__ . PHP_EOL;
    }
}

Dockerfile.php7

FROM php:7.0-alpine
COPY . .
ENTRYPOINT ["php", "a.php"]

Dockerfile.php8

FROM php:8.3-alpine
COPY . .
ENTRYPOINT ["php", "a.php"]

run-test.sh

docker build --quiet --file ./Dockerfile.php7 --tag demo-php-70 .
docker build --quiet --file ./Dockerfile.php8 --tag demo-php-83 .

docker run demo-php-70 || echo "Errored."
echo "---"
docker run demo-php-83 || echo "Errored."

unconditional.php

<?php

class Already_Defined {
    public function __construct() {
        echo 'Initialized from ' . __FILE__ . PHP_EOL;
    }
}