Hiring guide for PHP Engineers

PHP Developer Hiring Guide

PHP, which stands for Hypertext Preprocessor, is a popular open-source server-side scripting language widely used for web development. It is embedded into HTML and is particularly suited for creating dynamic web pages and applications. PHP can be used to manage databases, maintain sessions, handle data, and even create entire e-commerce sites. It supports a wide range of databases like MySQL, Oracle, and MS Access among others. PHP scripts are executed on the server and the result is returned to the browser as plain HTML. It also offers various features such as error handling, form handling, file uploading and more.

Ask the right questions secure the right PHP talent among an increasingly shrinking pool of talent.

First 20 minutes

General PHP app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in PHP application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you declare a variable in PHP?
You declare a variable in PHP by using the dollar sign ($) followed by the variable name. For example, $variableName = 'Hello, World!';
What are the different types of arrays in PHP?
There are three types of arrays in PHP: Indexed arrays, Associative arrays, and Multidimensional arrays.
Describe the difference between 'echo' and 'print' in PHP.
'echo' and 'print' are both used to output data to the screen. The differences are small: 'echo' has no return value while 'print' has a return value of 1 so it can be used in expressions. 'echo' can take multiple parameters while 'print' can take one argument.
How would you create a session in PHP?
You can create a session in PHP by using the session_start() function. This function creates a new session or resumes the current one. You can then set session variables by using the $_SESSION superglobal array.
What are the different types of errors in PHP?
There are three types of errors in PHP: Notices, Warnings, and Fatal errors.
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What you’re looking for early on

Does the candidate have a strong understanding of PHP and its associated frameworks?
Has the candidate demonstrated problem-solving skills during the interview?
Is the candidate familiar with the latest web technologies, such as HTML5, CSS3 and JavaScript?
Can the candidate work well as part of a team?

Next 20 minutes

Specific PHP development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

Describe the difference between GET and POST methods in PHP.
GET displays the submitted data as part of the URL, during normal navigation, whereas POST does not. Also, 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.
How would you handle exceptions in PHP?
Exceptions in PHP are handled using a try, catch, and finally blocks. Code within the try block is executed, and if an exception occurs, the code execution is passed to the catch block. The finally block is optional and contains code that will always be executed, regardless of whether an exception was thrown.
What are magic methods in PHP?
Magic methods in PHP are special functions which are always defined inside classes, starting with two underscores (__). For example, __construct, __destruct, __call, __get, __set are some of the magic methods which allow a developer to override default PHP behavior.
Describe the difference between == and === operator in PHP.
In PHP, == is the equal operator and it checks if the values of two operands are equal or not. If yes, then the condition becomes true. On the other hand, === is the identical operator and it checks if the values and their types are equal or not. If yes, then the condition becomes true.
How would you prevent SQL Injection in PHP?
SQL Injection can be prevented in PHP by using prepared statements and parameterized queries. Both of these methods ensure that an attacker is not able to change the intent of a query, even if SQL commands are inserted by an attacker.
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The ideal back-end app developer

What you’re looking to see on the PHP engineer at this point.

At this point, a skilled PHP engineer should demonstrate strong problem-solving abilities, proficiency in PHP programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with PHP.

What does the following PHP code do?
This code prints the string 'Hello, World!' to the standard output.
What will be the output of the following PHP code?
The output will be 15. The code adds the values of variables $x and $y and prints the result.
What does the following PHP code do?
This code iterates over each element in the array and prints its value. The output will be 12345.
What does the following PHP code do?
This code creates a class named 'MyClass' with a public property 'prop1'. Then it creates an object of 'MyClass' and prints the value of 'prop1'. The output will be 'I'm a class property!'.

Wrap-up questions

Final candidate for PHP Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle PHP application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What are Traits in PHP?
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.
Describe the difference between include and require in PHP.
The difference between include and require arises when the file being included cannot be found: include will emit a warning (E_WARNING) and the script will continue, whereas require will emit a fatal error (E_COMPILE_ERROR) and halt the script.
How would you implement form validation in PHP?
Form validation can be implemented in PHP by using the filter_var() function. It can be used to validate both the type and format of the input data.

PHP application related

Product Perfect's PHP development capabilities

Beyond hiring for your PHP engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in PHP projects, and can engage in multiple capacities.