How to reload code changes in CodeIgniter with RabbitMQ?

I am using CodeIgniter framework with RabbitMQ for doing time consuming activities such as sending emails, generating PDFs.

Whenever I change a code in the PHP files, say library or controller, until I restart the Apache, the old code is being executed by the RabbitMQ. How to resolve this?

The function in Controller,

public function receive()
{
    $this->db->reconnect();
    $connection = new AMQPStreamConnection('localhost', 5672, 'guest', 'guest');
    $channel = $connection->channel();
    $channel->queue_declare('generate_pdf', false, false, false, false);
    echo "[*] Started listening to connections... To exit press CTRL+C\n";
    $generate_pdf = function ($data)
    {
        $this->generatepdf->generate($data); // Generatepdf.php library -> generate() function
    };
    $channel->basic_qos(null, 1, null);
    $channel->basic_consume('generate_pdf', '', false, true, false, false, $generate_pdf)

    while ($channel->is_consuming())
    {
        $channel->wait();
    }
}

Starting this in termimal,

php index.php Controllerfile.php receive

This works fine as expected. So when a job is pushed to the queue, the generate() function in the library file Generatepdf.php is called and the execution is done.

However, if I modify the generate() function thru an editor or I re-upload the file with changes, the changes does not reflect until I restart the Apache server.

Function definition before changes:

public function generate()
{
    echo "Hello the data is 250";
}

Output: Hello the data is 250

Function definition after the change:

public function generate()
{
    echo "Hello the data is 251";
}

Output before restarting Apache: Hello the data is 250

Output after restarting Apache: Hello the data is 251

Why does this happen? How can I made the execution to refresh the changes in the file?

from How to reload code changes in CodeIgniter with RabbitMQ?