Installing and Configuring PHP

Introduction

Client-side programming languages, like JavaScript, are handled entirely by the browser. To do this, browsers like Firefox, Chrome, Safari, Edge, and others include JavaScript engines that use just-in-time compilers to execute JavaScript code (see JavaScript Engine, Mozilla).

From an end user's perspective, you basically install JavaScript when you install a web browser.

PHP, on the other hand, is a server-side programming language. This means it must be installed on the server. Unlike with JavaScript, the browser does not execute PHP directly; instead, the web server processes the PHP and sends the resulting HTML or other content to the browser.

From a system or web administrator's perspective, this means that PHP has be installed and configured to work with the web/HTTP server. In our case, we have to install and configure PHP on our virtual instances to work with the Apache web server software.

One of the primary uses of PHP is to interact with databases, like MySQL, MariaDB, PostgreSQL, etc., in order to create data-based page content. To begin to set this up, we have to:

  1. Install PHP and relevant Apache modules
  2. Configure PHP and relevant modules to work with Apache
  3. Configure PHP and relevant modules to work with MySQL

Install PHP

As usual, we will use apt install to install PHP and relevant modules. Then we will restart Apache using the systemctl command. Use apt show [package_name] to read more about each package we will install. The first command below installs the php and the libapache2-mod-php packages. The latter package is used to create a connection between PHP and the Apache web server.

sudo apt install php libapache2-mod-php
sudo systemctl restart apache2

Once installed, you want to confirm the installed version with the following command. This is because other software (e.g., WordPress, etc.) might require a specific version before that other software to work.

php -v

After we restart Apache, we need to check its status and see if there are any errors in the log output:

systemctl status apache2

Check Install

Next we check that PHP has been installed and that it's working with Apache. We can create a small PHP file in our web document root. To do that, we cd to the document root, /var/www/html/, and create a file called info.php:

cd /var/www/html/
sudo nano info.php

In that file, add the following text, then save and close the file:

<?php
phpinfo();
?>

Now visit that file using the public IP address for your server. If the public IP address for my virtual machine is 55.333.55.33, then in Firefox, Chrome, etc, I would open:

http://55.333.55.333/info.php

Again, be sure to replace the IP below with the IP address of your server and be sure to use http and not https.

You should see a page that provides system information about PHP, Apache, and the server. The top of the page should look like Figure 1 below:

PHP install page
Fig. 1. A screenshot of the title of the PHP install page.

Once you've confirmed that PHP is installed and functioning, you should delete it since it exposes detailed systems information:

sudo rm /var/www/html/info.php

Basic Configurations

By default, when Apache serves a web page, it looks for a file titled index.html and serves that, even if it does not display that file in the URL bar. Thus, http://example.com/ actually resolves to http://example.com/index.html in such cases. However, if our plan is to provide for PHP, we want Apache to default to a file titled index.php instead of index.html file. In these cases, http://example.com/ would actually resolves to http://example.com/index.php.

To configure that, we need to edit the dir.conf file in the /etc/apache2/mods-enabled/ directory. In that file there is a line that starts with DirectoryIndex followed by a list of files. The first file listed in that line is index.html, and then there are a series of other files that Apache looks for in the order listed. Apache checks that list list and prioritizes these in order of appearance on the list. If any of those files exist in the document root, then Apache serves those before proceeding to the next. We want Apache to prioritize the index.php file first and index.html second. Before modifying this file, it's good practice to create a backup of the original. So we will use the cp command to create a copy with a new name, and then we will use nano to edit the file.

cd /etc/apache2/mods-enabled/
sudo cp dir.conf dir.conf.bak
sudo nano dir.conf

Next we change the line to this, so that index.php is first in line:

DirectoryIndex index.php index.html index.cgi index.pl index.xhtml index.htm

Whenever we make a configuration change, we should use the apachectl command to check our configuration:

apachectl configtest

If we get a Syntax Ok message, we can reload the Apache configuration, restart the service, and check its status:

sudo systemctl reload apache2
sudo systemctl restart apache2
systemctl status apache2

Create an index.php File

Now create a basic PHP page. cd back to the Apache document root directory and use nano to create and open an index.php file:

cd /var/www/html/
sudo nano index.php

Let's add some HTML and PHP to it. We will add PHP that functions as a simple browser detector. Add the following code:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Browser Detector</title>
</head>
<body>
    <h1>Browser & OS Detection</h1>
    <p>You are using the following browser to view this site:</p>

    <?php
    $user_agent = $_SERVER['HTTP_USER_AGENT'];

    // Browser Detection
    if (stripos($user_agent, 'Edge') !== false) {
        $browser = 'Microsoft Edge';
    } elseif (stripos($user_agent, 'Firefox') !== false) {
        $browser = 'Mozilla Firefox';
    } elseif (stripos($user_agent, 'Chrome') !== false && stripos($user_agent, 'Chromium') === false) {
        $browser = 'Google Chrome';
    } elseif (stripos($user_agent, 'Chromium') !== false) {
        $browser = 'Chromium';
    } elseif (stripos($user_agent, 'Opera Mini') !== false) {
        $browser = 'Opera Mini';
    } elseif (stripos($user_agent, 'Opera') !== false || stripos($user_agent, 'OPR') !== false) {
        $browser = 'Opera';
    } elseif (stripos($user_agent, 'Safari') !== false && stripos($user_agent, 'Chrome') === false) {
        $browser = 'Safari';
    } else {
        $browser = 'Unknown Browser';
    }

    // OS Detection
    if (stripos($user_agent, 'Windows') !== false) {
        $os = 'Windows';
    } elseif (stripos($user_agent, 'Mac') !== false || stripos($user_agent, 'Macintosh') !== false) {
        $os = 'Mac';
    } elseif (stripos($user_agent, 'Linux') !== false) {
        $os = 'Linux';
    } elseif (stripos($user_agent, 'iOS') !== false || stripos($user_agent, 'iPhone') !== false || stripos($user_agent, 'iPad') !== false) {
        $os = 'iOS';
    } elseif (stripos($user_agent, 'Android') !== false) {
        $os = 'Android';
    } else {
        $os = 'Unknown OS';
    }

    // Output Result
    echo "<p>Your browser is <strong>$browser</strong> and your operating system is <strong>$os</strong>.</p>";
    ?>

</body>
</html>

Next, save the file and exit nano. In your browser, visit your site at its public IP address (again, replace your server's IP address):

http://55.333.55.333/

Although your index.html file still exists in your document root, Apache now returns the index.php file instead. If for some reason PHP fails, then the index.html file would be served next since that's what is listed next in the dir.conf file on the DirectoryIndex line.

Conclusion

In this section, we installed PHP and configured it to work with Apache. We also created a simple PHP test page that reported our browser user agent information on our website.

In the next section, we'll learn how to complete the LAMP stack by adding the MySQL relational database to our setup.