The KISS Principle with PHP Examples

In the ever-evolving world of software development, one principle remains a golden rule: “Keep It Simple, Stupid” or KISS. The KISS principle emphasizes the importance of simplicity in design and implementation. It advocates for solutions that are straightforward, easy to understand, and uncomplicated.

While it might sound like common sense, the art of keeping things simple is often overlooked in the quest for complexity.

Also, it is common for developers to complicate readability in the hunt for more fancy, newer, and advanced solutions and concepts.

Instead of thinking about how to do things shortest or fighting for bytes of RAM, when it’s not the case think about the ones who will come after you to alter your code.

Understanding KISS

KISS in my opinion can be summed up with a few key principles:

  1. Simplicity: Strive for the simplest solution that meets the requirements. Avoid overengineering or adding unnecessary complexity.
  2. Clarity: The code should be clear and easy to read. Self-explanatory variable names, concise methods, and minimal nested structures all contribute to clarity.
  3. Maintainability: Simple code is easier to maintain and less prone to bugs. When a problem arises, it’s easier to diagnose and fix.

First PHP example – academic calculations

Let’s illustrate the KISS principle with a PHP example. Suppose we need a function to calculate the factorial of a number.

function factorial($n)
    if ($n <= 1) {
        return 1;
    } else {
        return $n * factorial($n - 1);

This recursive function calculates the factorial of a number using a common algorithm. It works, it was probably taught in the University, but it’s not the simplest or most readable solution.

A simpler and more readable approach is to use a loop instead of recursion:

function factorial($n)
    $result = 1;
    for ($i = 1; $i <= $n; $i++) {
        $result *= $i;
    return $result;

This code is easier to understand because it doesn’t involve recursive calls. It calculates the factorial iteratively, making it more straightforward for anyone who reads the code.

Second PHP example – overusing ternary

Another common case is overusing ternary operators.

Consider the following complex ternary expression:

$result = ($condition1 && $condition2) ? 'Both conditions are met' : (($condition1 || $condition2) ? 'At least one condition is met' : 'Neither condition is met');

While this ternary expression is concise, and “cool”, it can be challenging to understand at a glance. Let’s simplify it and improve readability by using a separate if statements:

if ($condition1 && $condition2) {
    $result = 'Both conditions are met';
} elseif ($condition1 || $condition2) {
    $result = 'At least one condition is met';
} else {
    $result = 'Neither condition is met';

By breaking the complex ternary expression into separate if statements, we make the code more explicit and easier to follow. Each condition and its corresponding outcome are clearly separated, which enhances code readability and maintainability.

Why? So the Benefits of Simplicity

By following the KISS principle and opting for the simpler solution, we gain several benefits:

  • Readability: The code is easier for developers (including your future self) to read and understand.
  • Maintainability: It’s easier to maintain and modify when requirements change or bugs need fixing.
  • Reduced Risk: Simpler code is less likely to contain hidden bugs, reducing the risk of unexpected issues.


The KISS principle reminds us to prioritize simplicity in software development. It’s not about sacrificing functionality but about finding elegant, straightforward solutions to problems. By keeping code simple and understandable, we improve readability, maintainability, and efficiency. The PHP example of calculating factorials demonstrates how embracing simplicity can lead to better, more maintainable code.

In your own projects, remember the KISS principle: Keep It Simple, Stupid. Your codebase and fellow developers will thank you for it.

You might be interested in exploring other principles, like SOLID ones. Start from Single Responsibility Principle (SRP).

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