8. Embedding the source code

It looks like the apache image is working but needs a website to display. Create a small web application and run it inside the container.

Create a PHP app

For this lab you’re going to need a small PHP app consisting of two files.

First, create a directory for the app’s files called php-app.

Then, inside that directory, create a new file named index.php with the following content:

<?php
echo "Welcome to Docker (my young padawan)!";
?>

Lastly, create another file named db.php with the following content:

<?php
$servername = "mariadb-container-with-existing-external-volume";
$username = "peter";
$password = "venkman";

// Create connection
$conn = new mysqli($servername, $username, $password);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}
echo "Connected successfully";
?>

That’s it for the app part.

Mounting the dev environment into your Docker container

Make sure you’re outside that freshly created app directory when you execute the next commands.

Now mount the php-app as the host directory into your container:

Linux:

docker run -d --name apache-php -v $(pwd)/php-app:/var/www/html php:8-apache

Windows (Git Bash):

MSYS_NO_PATHCONV=1 docker run -d --name apache-php -v $(pwd)/php-app/:/var/www/html php:8-apache

You can now check whether the error is still present.

Port forwarding for your Docker container

Docker is able to forward any port you specify to your local machine by using -p <host-port>:<container-port>. This is great but also has the possibility of causing port trouble.

Imagine you have a local httpd service running on port 8080, and you are forwarding this same port to your Docker instance.

So first, let us check out if port 8080 is occupied:

In Linux or macOS do the following:

lsof -i:8080

or in Windows (Git Bash):

netstat -aon | findstr :8080 | findstr LISTENING

If you get an output, this means port 8080 is used. In that case just us a different port, like 8888, in the examples below.

Now run the image using the -p flag:

Linux/Webshell:

docker stop apache-php
docker rm apache-php
docker run -p 8080:80 -d --name apache-php -v $(pwd)/php-app:/var/www/html php:8-apache

Windows (Git Bash):

docker stop apache-php
docker rm apache-php
MSYS_NO_PATHCONV=1 docker run -p 8080:80 -d --name apache-php -v $(pwd)/php-app/:/var/www/html php:8-apache

If you take a look into docker ps you’ll find an interesting change for the PORTS column

docker ps

CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                NAMES
6b0721fa6103        php:8-apache        "docker-php-entryp..."   5 seconds ago       Up 4 seconds        0.0.0.0:8080->80/tcp   apache-php
50197361e87b        mariadb             "docker-entrypoint..."   2 hours ago         Up 2 hours          3306/tcp             mariadb-container-with-existing-external-volume

You see that every request coming to port 8080 on your local machine is forwarded to your Docker instance’s port 80. If you now type http://LOCALHOST:8080/index.php in your browser you should get the message:
“Welcome to Docker…”.
http://LOCALHOST:8080/db.php will produce an error. This is on purpose. Please be patient until the end of lab 10!