Computer programs are written for machine reading. We have to write them in a certain format which will be compiled for the machine to understand. But often those written codes are not easy to follow for people other than programmers. In order to show those codes in an informal way so that humans can also understand, we prepare pseudocode. Though it is not an actual programming language code, pseudocode has similar structural conventions of a programming language. Since pseudocode does not run as a real program, there is no standard way of writing a pseudocode. We can follow our own way of writing a pseudocode.

Here is the pseudocode for our algorithm to find a book:

Algorithm FindABook(L,book_name) 
  Input: list of Books L & name of the search book_name 
  Output: False if not found or position of the book we are looking for. 

  if L.size = 0 return null 
  found := false 
  for each item in L, do 
    if item = book_name, then 
      found := position of the item 
  return found 

Now, let us examine the pseudocode we have written. We are supplying a list of books and a name that we are searching. We are running a foreach loop to iterate each of the books and matching with the book name we are searching. If it is found, we are returning the position of the book where we found it, false otherwise. So, we have written a pseudocode to find a book name from our book list. But what about the other remaining books? How do we continue our search till all books are found and placed on the right shelf?:

  Algorithm placeAllBooks 
    Input: list of Ordered Books OL, List of received books L 
    Output: nothing. 


    for each book_name in OL, do 
       if FindABook(L,book_name), then 
         remove the book from the list L 
         place it to the bookshelf 

Now we have the complete pseudocode for our algorithm of solving the book organization problem. Here, we are going through the list of ordered books and finding the book in the delivered section. If the book is found, we are removing it from the list and placing it to the right shelf.

This simple approach of writing pseudocode can help us solve more complex problems in a structured manner. Since pseudocodes are independent of programming languages and platforms, algorithms are expressed as pseudocode most of the time.

We are now going to convert our pseudocodes to actual PHP 7 codes as shown:

function findABook(Array $bookList, String $bookName) { 
    $found = FALSE; 

    foreach($bookList as $index => $book) { 
        if($book === $bookName) { 
             $found = $index; 
             break; 
        } 
    } 
    return $found; 
} 

function placeAllBooks(Array $orderedBooks, Array &$bookList) { 
    foreach ($orderedBooks as $book) { 
    $bookFound = findABook($bookList, $book); 
    if($bookFound !== FALSE) { 
        array_splice($bookList, $bookFound, 1); 
    } 
  } 
} 

$bookList = ['PHP','MySQL','PGSQL','Oracle','Java']; 
$orderedBooks = ['MySQL','PGSQL','Java']; 

placeAllBooks($orderedBooks, $bookList);
echo implode(",", $bookList); 

Let us now understand what is happening in the preceding code. First we have defined a new function, findABook at the beginning of the code. The function is defined with two parameters. One is Array $bookList and the other is String $bookName. At the beginning of the function we are initializing the $found to FALSE, which means nothing has been found yet. The foreach loop iterates through the book list array $bookList and for each book, it matches with our provided book name $bookName. If the book name that we are looking for matches with the book in the $bookList, we are assigning the index (where we found the match) to our $found variable. Since we have found it, there is no point in continuing the loop. So, we have used the break command to get out of the loop. Just out of the loop we are returning our $found variable. If the book was found, usually $found will return any integer value greater than 0, else it will return false:

function placeAllBooks(Array $orderedBooks, Array &$bookList) { 
    foreach ($orderedBooks as $book) { 
    $bookFound = findABook($bookList, $book); 
    if($bookFound !== FALSE) { 
        array_splice($bookList, $bookFound, 1); 
    } 
  } 
} 

This particular function placeAllBooks actually iterates through our ordered books $orderedBooks. We are iterating our ordered book list and searching each book in our delivered list using the findABook function. If the book is found in the ordered list ($bookFound !== FALSE), we are removing that book from the delivered book list using the array_splice() function of PHP:

$bookList = ['PHP','MySQL','PGSQL','Oracle','Java'];
$orderedBooks = ['MySQL','PGSQL','Java'];

These two lines actually shows two PHP arrays which are used for the list of books we have received, $bookList and the list of books we have actually ordered $orderedBooks. We are just using some dummy data to test our implemented code as shown:

placeAllBooks($orderedBooks, $bookList);

The last part of our code actually calls the function placeAllBooks to perform the whole operation of checking each book searching for it in our received books and removing it, if it is in the list. So basically, we have implemented our pseudocode to an actual PHP code which we can use to solve our problem.