If we consider our real-life situation with computers, we also use different sorts of arrangements of our belongings and data so that we can use them efficiently or find them easily when needed. What if we enter our phone contact book in a random order? Will we be able to find a contact easily? We might end up searching each and every contact in the book as the contacts are not arranged in a particular order. Just consider the following two images:

One shows that the books are scattered and finding a particular book will take time as the books are not organized. The other one shows that the books are organized in a stack. Not only does the second image show that we are using the space smartly, but also the searching of books becomes easier.

Let us consider another example. We are going to buy tickets for an important football match. There are thousands of people waiting for the ticket booth to open. Tickets are going to be distributed on a first come first served basis. If we consider the following two images, which one is the best way of handling such a big crowd?:

The left image clearly shows that there is no proper order and there is no way to know who came first to get the tickets. But if we knew that people were waiting in a structured way, in a line, or queue, then it will be easier to handle the crowd and we will hand over the tickets to whoever came first. This is a common phenomenon known as a queue which is heavily used in the programming world. Programming terms are not generated from outside the world. In fact, the majority of the data structures are inspired from real life and they use the same terms most of the times. Whether we are preparing our task list, contact list, book piles, diet charting, preparing a family tree, or organization hierarchy, we are basically using different arrangement techniques which are known as data structures in the computing world.

We have talked a little about data structures so far but what about algorithms? Don't we use any algorithms in our daily lives? Definitely we do. Whenever we are searching for a contact from our old phone book, we are definitely not searching from the beginning. If we are searching for Tom, we will not search the page where it says A, B, or C. We are directly going to the page T and will find if Tom is listed there or not. Or, if we need to find a doctor from a telephone directory, we will definitely not search in the foods section. If we consider the phone book or telephone directory as data structures, then the way we search for particular information is known as algorithms. While data structures help us to use data efficiently, algorithms help us to perform different operations on those data efficiently. For example, if we have 100,000 entries in our phone directory, searching a particular entry from the beginning might take a long time. But, if we know the doctors are listed from page 200 to 220, we can search only those pages to save our time by searching a small section rather than the full directory:

We can also consider a different way of searching for a doctor. While the previous paragraph takes the approach of searching a particular section of the directory, we can even search alphabetically within the directory, like the way we search a dictionary for a word. That might even reduce the time and entries for our searching. There can be many different approaches to find solutions of a problem, and each of the approaches can be named as algorithms. From the earlier discussion we can say that for a particular problem or task, there can be multiple ways or algorithms to perform. Then which one should we consider to use? We are going to discuss that very soon. Before moving to that point, we are going to focus on PHP data types and Abstract Data Types (ADT). In order to grasp the data structure concept, we must have a strong understanding of PHP data types and ADT.