Programming languages or PHP Interview Questions

Programming languages that are popular by businesses

·        What’s the difference between the include () and require () functions?

They both include a specific file but on require the process exits with a fatal error if the file can’t be included, while include statement may still pass and jump to the next step in the execution.

·        How can we get the IP address of the client?

This question might show you how playful and creative the candidate is because there are many options. $_SERVER["REMOTE_ADDR"]; is the easiest solution

·        What’s the difference between unset() and unlink()

unset() sets a variable to “undefined” while unlink() deletes a file we pass to it from the file system.

·        What are the main error types in PHP and how do they differ?

In PHP there are three main types of errors:

·         Notices – Simple, non-critical errors that are occurred during the script execution. An example of a Notice would be accessing an undefined variable.

·         Warnings – more important errors than Notices, however the scripts continue the execution. An example would be include () a file that does not exist.

·         Fatal – this type of error causes a termination of the script execution when it occurs. An example of a Fatal error would be accessing a property of a non-existent object or require() a non-existent file.

What is the difference between GET and POST?
GET displays the submitted data as part of the URL, during POST this information is not shown as it’s encoded in the request.

·         GET can handle a maximum of 2048 characters, POST has no such restrictions.

·         GET allows only ASCII data, POST has no restrictions, binary data are also allowed.

·         Normally GET is used to retrieve data while POST to insert and update.

·         How can you enable error reporting in PHP?
Check if “display_errors” is equal “on” in the php.ini or declare “ini_set('display_errors', 1)” in your script.
Then, include “error_reporting(E_ALL)” in your code to display all types of error messages during the script execution.

·         Enabling error messages is very important especially during the debugging process as one can instantly get the exact line that is producing the error and can see also if the script in general is behaving correctly.

What are Traits?

Traits are a mechanism that allows you to create reusable code in languages like PHP where multiple inheritance is not supported. A Trait cannot be instantiated on its own.

 Can you extend a Final defined class?

No, you cannot extend a Final defined class. A Final class or method declaration prevents child class or method overriding.

What are the __construct() and __destruct() methods in a PHP class?

All objects in PHP have Constructor and Destructor methods built-in. The Constructor method is called immediately after a new instance of the class is being created, and it’s used to initialize class properties. The Destructor method takes no parameters

 How we can get the number of elements in an array?

The count() function is used to return the number of elements in an array.

Understanding of arrays and array related helper functions is important for any PHP developer.

Suppose that you have to implement a class named Dragonball. This class must have an attribute named ballCount (which starts from 0) and a method iFoundaBall. When iFoundaBall is called, ballCount is increased by one. If the value of ballCount is equal to seven, then the message you can ask your wish is printed, and ballCount is reset to 0. How would you implement this class?

<?php

class dragonBall{

  private $ballCount;

  public function __construct(){

    $this->ballCount=0;

  }

  public function iFoundaBall(){

    $this->ballCount++;

    if($this->ballCount===7){

      echo "You can ask for your wish.";

      $this->ballCount=0;

    }

  }

}

?>

 What are the 3 scope levels available in PHP and how would you define them?

Private – Visible only in its own class
Public – Visible to any other code accessing the class
Protected – Visible only to classes parent(s) and classes that extend the current class

This is important for any PHP developer to know because it shows an understanding that building applications is more than just being able to write code. One must also have an understanding about privileges and accessibility of that code. There are times protected variables or methods are extremely important, and an understanding of scope is needed to protect the integrity of the data in your application along with provide a clear path through the code.

 What are getters and setters and why are they important?

Getters and setters are methods used to declare or obtain the values of variables, usually private ones. They are important because it allows for a central location that is able to handle data prior to declaring it or returning it to the developer. Within a getter or setter one is able to consistently handle data that will eventually be passed into variable or additional functions. An example of this would be a user’s name. If a setter is not being used and the developer is just declaring the $userName variable by hand, you could end up with results as such: "kevin", "KEVIN", "KeViN", "", etc. With a setter, the developer can not only adjust the value, for example, ucfirst($userName), but can also handle situations where the data is not valid such as the example where "" is passed. The same applies to a getter – when the data is being returned, it can be modifyed the results to include strtoupper($userName) for proper formatting further up the chain.

 What does MVC stand for and what does each component do?

MVC stands for Model View Controller.
The controller handles data passed to it by the view and also passes data to the view. It’s responsible for interpretation of the data sent by the view and dispersing that data to the appropriate models awaiting results to pass back to the view. Very little, if any business logic should be occurring in the controller.

The model’s job is to handle specific tasks related to a specific area of the application or functionality. Models will communicate directly with your database or other storage system and will handle business logic related to the results.

The view is passed data by the controller and is displayed to the user.

Overall, this question is worth knowing as the MVC design pattern has been used a lot in the last few years and is a very good design pattern to know. Even with more advanced flows that go down to repositories and entities, they still are following the same basic idea for the Controller and View. The Model is typically just split out into multiple components to handle specific tasks related to database data, business logic etc. The MVC design pattern helps draw a better understanding of what is being used, as a whole, in the industry.

What are SQL Injections, how do you prevent them and what are the best practices?

SQL injections are a method to alter a query in a SQL statement send to the database server. That modified query then might leak information like username/password combinations and can help the intruder to further compromise the server.

To prevent SQL injections, one should always check & escape all user input. In PHP, this is easily forgotten due to the easy access to $_GET & $_POST, and is often forgotten by inexperienced developers. But there are also many other ways that users can manipulate variables used in a SQL query through cookies or even uploaded files (filenames). The only real protection is to use prepared statements everywhere consistently.

Do not use any of the mysql_* functions which have been deprecated since PHP 5.5 ,but rather use PDO, as it allows you to use other servers than MySQL out of the box. mysqli_* are still an option, but there is no real reason nowadays not to use PDO, ODBC or DBA to get real abstraction. Ideally you want to use Doctrine or Propel to get rid of writing SQL queries all together and use object-relational mapping which binds rows from the database to objects in the application.

What does the following code output?

$  $i = 016;

e  echo $i / 2;

The Output should be 7. The leading zero indicates an octal number in PHP, so the number evaluates to the decimal number 14 instead to decimal 16

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