Declarative Programming in PHP: A Comprehensive Overview and Comparison with Imperative Programming

5 min readMay 5, 2023

Introduction:

PHP is one of the most popular programming languages, especially in web development. It is widely used for building dynamic websites and applications. PHP was initially designed as an imperative language, which means that developers had to write code that describes the exact steps the computer needs to take to accomplish a task. However, in recent years, there has been an increasing interest in declarative programming, a paradigm that allows developers to focus on describing what they want the program to do, rather than how to do it. In this article, we will explore declarative programming in PHP and compare it with imperative programming. We will provide examples for each and analyze the pros and cons of each approach.

Declarative Programming in PHP:

Declarative programming is a programming paradigm that focuses on describing the desired result rather than specifying the exact steps that need to be taken to achieve it. In declarative programming, developers write code that describes the relationships and constraints between different parts of the program, without specifying the exact order in which they should be executed. This allows the computer to use its own algorithms to optimize the execution of the program. Here are three examples of declarative programming in PHP:

1. SQL queries:

SQL is a declarative language that allows developers to describe the data they want to retrieve from a database, rather than specifying the exact steps the database needs to take to retrieve it. For example, the following SQL query retrieves all the customers whose last name is Smith:

SELECT * FROM customers WHERE last_name = ‘Smith’;

2. Functional programming:

Functional programming is a declarative programming paradigm that focuses on describing the relationships between functions. In PHP, functional programming can be achieved using higher-order functions, closures, and lambda functions. For example, the following code uses the array_map() function to apply a function to every element of an array:

$numbers = [1, 2, 3, 4, 5]; $square = function($n) { return $n * $n; };
$squared_numbers = array_map($square, $numbers);

3. Template engines:

Template engines are tools that allow developers to separate the presentation logic from the business logic in web applications. They provide a declarative way of describing how the data should be displayed, without specifying the exact steps the computer needs to take to display it. In PHP, some popular template engines include Smarty, Twig, and Blade.

Imperative Programming in PHP:

Imperative programming is a programming paradigm that focuses on describing the exact steps the computer needs to take to accomplish a task. In imperative programming, developers write code that describes the control flow of the program, using statements like if, while, for, and switch. Here are three examples of imperative programming in PHP:

1. Procedural programming:

Procedural programming is a programming paradigm that focuses on describing the steps of a program in terms of procedures or functions. In PHP, procedural programming is often used for small to medium-sized projects. For example, the following code uses a while loop to print the first ten numbers:

$i = 1; while ($i <= 10) { echo $i; $i++; }

2. Object-oriented programming:

Object-oriented programming is a programming paradigm that focuses on describing the relationships between objects. In PHP, object-oriented programming is often used for large and complex projects. For example, the following code creates a class that represents a car:

class Car {

  private $make; 
  private $model;
  private $year;

  public function __construct($make, $model, $year) { 
    $this->make = $make;
    $this->model = $model;
    $this->year = $year;
  }

  public function getMake() { return $this->make; }

  public function getModel() { return $this->model; }

  public function getYear() { return $this->year; } 

}

3. Event-driven programming:

Event-driven programming is a programming paradigm that focuses on describing the behavior of a program in response to events. In PHP, event-driven programming is often used for web applications that need to respond to user input. For example, the following code uses the jQuery library to handle a button click event:

$(‘button’).click(function() { 
  alert(‘Button clicked’);
});

Comparison of Declarative Programming and Imperative Programming:

Declarative programming and imperative programming have different approaches to problem-solving. Declarative programming focuses on describing what the program should do, while imperative programming focuses on describing how to do it. Here are some pros and cons of each approach: