Apache is known as one of the popular web servers. It is an open-source tool introduced by Apache Software Foundation open source community. Apache server is often preferred for most web servers. 

Web server is where the data is stored and is a computer. Web servers accept the requests sent by the users and send appropriate responses to those requests. They are connected to the internet. They have unique IP addresses for easy recognition. These IDs are a series of four numbers ranging from 0 to 256 that are separated by periods.

Apache is the most used web server application worldwide and is most popular in the commercial web server market. Apache is most used on Unix platforms. It can also be run on Windows, OS/2, OS X, etc. The word Apache is derived from the American tribe named ‘Apache’.

Apache is a process-based modular web server application that creates a new thread for each simultaneous connection. It supports various valuable features. Many of the processes are compiled as separate modules. It extends the core functionalities. 

It acts as a server-side programming language. It supports an authentication mechanism. Apache allows you to serve different websites through a single Apache web server with the help of virtual hosting. 

You can install Apache in multiple ways:

• As Apache is an open-source application, you can customize the installer as per your environment. Various vendors customize the configuration of Apache and its file location concerning the OS and other installed applications.
• Another method is developing and installing the Apache server from a source code rather than a vendor-based installer. Installing Apache from a source file works for all OS platforms.

Apache is a modular application where the authoritative administrator can choose the functionalities and install various modules as per their requirements. Apache supports DSO (Dynamic Shared Objects). It can compile all the modules as a DSO that exists separately from the main Apache file. 

The DSO approach is recommended along with Apache as it simplifies the tasks of adding, updating, or removing the modules from the Apache server configuration. Apache is capable of hosting multiple websites on the same web server, where you do not need to arrange separate Apache software and server machines for each website. This is achieved with the help of the VHost or the Virtual Host concept.

Apache configuration file provides you the liability of choosing the domain you require to host on the web server. These domains can be found separately on the configuration file of the Apache server. There are two types of Virtual Host in Apache:

• Name-based virtual host
• IP-based or address-based virtual host

Name-based Virtual Host

Through a name-based virtual host, you can use a single IP address for hosting multiple virtual sites. You can apply name-based virtual hosting by making the changes in the NameVirtualHost directive in the apache configuration file httpd.conf file. It is to set a single IP address that receives the Apache user sent requests from all the desired multiple websites.

IP-based Virtual Host

To configure the IP-based virtual host, you require more than one IP address. These multiple IP addresses must be configured on the server. Thus, the number of virtual hosts configured is proportional to the number of IP addresses configured on your server.

You can run PHP files on the Apache web server. To run PHP files on your web server, you must enable mod_php that allows Apache to interpret the PHP file. This interpretation of the PHP code is done by the PHP handlers in Apache and sends the HTML to your web server. PHP handlers in Apache are mod_php, CGI, suPHP, FastCGI.  

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