Drupal Interview Questions and Answers

Drupal is free and open source Content Management System (CMS).CMS framework written in PHP.  It enables you to organize, manage and publish content with ease and comes with a variety of customization option.

• Drupal is very powerful and can be used for building large, complex sites.
• Easy to install and easy to use
• It has lots of features including Search Engine Friendly URLs(SEF), categories, search function.
• It has lots of modules to extend your site’s functionality.
• Flexibility – you can easily turn your Drupal installation into a forum, blog, wiki and many other types of web sites.
• It is free to use and it is open source. Drupal can be easily installed and modified to change the source code to fit your needs.
• Lots of users and a large community find it easy to find solutions to your problems

Key features of Drupal are

• Upload Module: It enables users to attach different types of files to node types of your liking.
• Embedding: It enables to embed media within nodes that are hosted on your websites.
• Powerful templating system. Any XHTML or CSS template can be easily converted to Drupal
• Real multi-site-feature (only one installation for several sites)
• Any Kind of user groups & user permissions, OpenId compliant
• Can run membership and community sites, not only CMS etc
• Clear, high quality code and API (easy to integrate with other solutions etc)

• New Theme Engine
• CKEditor
• Mobile First from The Get-Go
• Loading speed
• Big pipe and views in core
• Multilingual
• Manage Configuration
• Easy Authoring
• Quick Edits
• Better Support For Accessibility
• Web services built in
• JavaScript Automated Testing
• Better Mark-up with HTML5
• Fields Galore

A Web content management system is content management system software, implemented as a Web application, for creating and managing HTML content. It is used to manage and control a large dynamic collection of Web material. A WCMS facilitates content creation, content control, editing, and essential Web maintenance functions. The software provides authoring tools designed to allow users with little knowledge of programming languages or markup languages to create and manage content with relative ease. Most systems use a database to store content, metadata, or artifacts that might be needed by the system. Content is frequently, but not universally, stored as XML, to facilitate reuse and enable flexible presentation options.

Most systems use server side caching boosting performance. This works best when the WCMS is not changed often but visits happen on a regular basis. Administration is typically done through browser-based interfaces, but some systems require the use of a fat client.

Drupal is often compared to a number of commercial content management systems including Crown Peak, ExpressionEngine, Clickability and Site Life in terms of capabilities. None of these systems offer the range of features that can be found in Drupal or the flexible, developer-friendly architecture that allows us to rapidly deploy dynamic web sites. In terms of sustainability, these platforms lack the innovative approach to development, with updates and new features continually being added to the platform. These systems typically do surpass Drupal in terms of out-of-the-box reporting and metrics tools, generally providing views of data that is also stored in other systems.

Through caching Drupal allows to speed up website using different configuration like page caching, block caching and lifetime for cached pages.

• Page Caching: It enables the entire HTML of each page to be stored in the database.  It reduces the amount of queries needed
• Block Caching: You can set the cache setting for a block in views, when block created by views
• Minimum cache lifetime: It is the amount of time before the page cache is cleared. On each cron run, page caches are cleared.
• Expiration of cached pages: It only applies for an external mechanism, for example, your browser cache or varnish

service.yml placed in the root directory in and all the services are defined here.

A patch is a file that contains a list of differences between one set of files, and another.  Through patches, all the changes in code like additions or deletions to Drupal core can be made. Also, patches can be used to make changes to another copy of the original or main file.

This is the global settings of the site.The database, URL structure, salt, encryption etc all the variables are defined here

PDO means PHP Data Object; it is a lean and consistent way to access databases. It allows developers to write portable code with ease.

Sub-themes are just like any other theme, with one difference: They inherit the parent theme’s resources. There are no limits on the chaining capabilities connecting sub-themes to their parents. A sub-theme can be a child of another sub-theme, and it can be branched and organized however you see fit. This is what gives sub-themes great potential.

Using content construction kit Drupal allows you to create multiple content types without any programming skills. And for each content type it allows customize theme template. You can have an article, story, slideshow, content type and so on.

Drupal comes with a built in taxonomy system. The taxonomy system allows you to categorize the nodes on your site. The taxonomy system allows you to define vocabularies allow you to organize your terms into groups. Each term is essentially a category. There is no limit to the number of vocabularies you can create. There is also no limit to the number of terms that you can include in each vocabulary. Your vocabulary can also have free tagging. So instead of entering specific terms ahead of time users may enter tags freely at the time the post is written and those tags automatically become terms in that vocabulary.

In a database Drupal stores information, and each information has its own database table.  For example, the basic information regarding the nodes of your site are stored and kept in the node table, and if you use the CCK module to add fields to your nodes, the field information is stored in a separate table.

The set of links, usually near the top of the page, that shows the path you followed to locate the current page. For example, it might show Home > Drupal > Current Events > News Articles, meaning that you started at the home page, clicked on “Drupal” in the menu, then selected “Current Events” in the sub-menu, and finally selected, “News Articles.” The term breadcrumbs are borrowed from Hansel and Gretel, who left crumbs of bread along their path so they could find their way back out of the forest.

Some of the commonly used PHP are

• Drupal
• Joomla
• WordPress
• TYPO3

DRUSH is a command line shell and UNIX scripting interface for Drupal

Modules are like plugin for your site.  It allows you to add different functions to your site such as polls, contact forms and search fields.  Some of the modules recommended are

• Views
• Token
• Ctools
• Quicktabs
• Pathauto

Distributions are full copies of Drupal, which includes Drupal Core, along with additional software as modules, themes, libraries and installation profiles. You can use distributions for

• Evaluating Drupal
• Demoing Drupal
• Learning Drupal
• Quickly binding Site

Allow the use of different database servers using the same code base.

Drupal provides a slim database abstraction layer to provide developers with the ability to support multiple database servers easily. The intent of this layer is to preserve the syntax and power of SQL as much as possible, while letting Drupal control the pieces of queries that need to be written differently for different servers and provide basic security checks.

Most Drupal database queries are performed by a call to db_query() or db_query_range(). Module authors should also consider using pager_query() for queries that return results that need to be presented on multiple pages, and tablesort_sql() for generating appropriate queries for sortable tables.

Some of the SEO modules available in Drupal are

• Pathauto
• Meta tags/ Node words
• Service Links
• Google Analytics
• Related Links
• Search 404
• Site map
• Url list

The term Drupal weight is used to describe the priority or order in which the function is processed, or block/ node is displayed.

A heavier (+10) weights will appear lower in lists while a lower weight (-10) will float to the top of lists.

Article type is a regular blog post on the site. We can select Article if we are writing an article or blog posts related to latest updates etc.

To execute commands or scripts automatically at specified time and date intervals, you have to use Drupal cron.

Drupal stores its information in the database like individual pages, registered users and so on.  For your Drupal site, database forms the back end; it supports MySQL /MariaDB, PostgreSQL and in Drupal 7, SQLite.

PSD files are the raw photoshop files used to generate the graphics in a theme. You need to convert the PSD to regular html/css theme, then you have to follow the steps for creating a drupal theme.Know more about file system in drupal theme

For Drupal content render arrays are the basic building blocks.  In Drupal, render arrays provide you a structured way to programmatically change the content before it is displayed.

This suite is a set of APIs and tools, and it makes easier to handle AJAX requests and tell the client what to do with them.

The files required for

• Theme: style.css, page.tpl.php, template.php, block.tpl.php
• Module: modulename.info, modulename.module, optional modulename.install

To drop the table you can use db_drop_table in install file.

Drupal is translated into all popular languages including

• Catalan
• French
• Hungarian
• Dutch

Every visitor to your site, whether they have an account and log in or visit the site anonymously, is considered a user to Drupal. Each user has a numeric user ID, and non-anonymous users also have a user name and an email address. Other information can also be associated with users by modules; for instance, if you use the core Profile module, you can define user profile fields to be associated with each user.

Anonymous users have a user ID of zero (0). The user with user ID one (1), which is the user account you create when you install Drupal, is special: that user has permission to do absolutely everything on the site.

Other users on your site can be assigned permissions via roles. To do this, you first need to create a role, which you might call “Content editor” or “Member”. Next, you will assign permissions to that role, to tell Drupal what that role can and can’t do on the site. Finally, you will grant certain users on your site your new role, which will mean that when those users are logged in, Drupal will let them do the actions you gave that role permission to do.

You can also assign permissions for the special built-in roles of “anonymous user” and “authenticated user”. Drupal permissions are quite flexible — you are allowed to assign permission for any task to any role, depending on the needs of your site.

Like with all open-source projects there is no commercial support available. Though, there is a vast online community for Drupal available via Forums and IRC online chat who are more than eager to answer your queries.

The standard Drupal installation contains a sample .htaccess file which supports clean URLs. It is easy to miss copying this file, because of the leading “dot”. So before trying to enable Clean URLs, make sure this file exists in your Drupal installation.

The core Drupal distribution provides a number of features, including

• Access statistics and logging
• Advanced search
• Blogs, books, comments, forums, and polls
• Caching and feature throttling for improved performance
• Descriptive URLs
• Multi-level menu system
• Multi-site support
• Multi-user content creation and editing
• OpenID support
• RSS feed and feed aggregator
• Security and new release update notification
• User profiles
• Various access control restrictions (user roles, IP addresses, email)
• Workflow tools (triggers and actions)