Comparing PHP and JavaScript

Scripting Languages with a difference

Both PHP and JavaScript are scripting languages. A scripting language is a special-purpose programming language that is used for automating tasks. PHP is designed to be a server-side scripting language, while JavaScript is mainly used for client-side scripting. PHP is one of the most commonly used server-side scripting languages on the web.  The most common use of JavaScript is on web pages. While the web browser is the most common host environment for JavaScript, JavaScript interpreters are also used in other tools and environments including Adobe Acrobat & Adobe Photoshop, server-side  Node.js, and NoSQL database Apache CouchDB to mention a few.

Interpreted Languages with a difference

Both PHP and JavaScript are interpreted languages. An interpreted language does not need compilation to bytecode as compiled languages such as Java do. Instead, an interpreted language is interpreted at runtime by the runtime engine (such as Zend engine in PHP).  Interpretation involves direct translation and running of script code without intermediate compilation. As an example, the PHP Zend Engine directly translates the PHP scripts into Zend opcodes or instruction machine code.  The benefit of an interpreted language is the flexibility it offers by skipping compilation. The difference between PHP and JavaScript is that while both started off by using only interpreters JavaScript has shifted from using interpreters to using just-in-time compilation. Most modern browsers such as   V8 JavaScript engine in Google Chrome browser use just-in-time compilation by compiling and caching frequently run code to avoid having to translate JavaScript each time the same code is run in a browser.    

Loosely or Weakly-Typed with a difference

Both PHP and JavaScript are weakly or loosely typed programming languages, which implies that variables are declared without specifying a variable type. While it does provide the latitude of not requiring a variable type, it also adds the likelihood of error. Both PHP and JavaScript have a type system and support commonly used data structures so that variables do get assigned a type when the code is run. PHP 7 introduced several new features in the type system including scalar types, type declarations for function parameters, return type declarations, typed properties, and a new directive strict_types for strict typing. In effect, if strict typing is used PHP scripts are not loosely typed and throw a TypeError if a value type differs from the declared type. JavaScript is a loosely typed language without provision for strict typing. ECMAScript 5, the JavaScript standard, introduced a strict mode with which some strict typing is made available such as setting properties on primitive values throws a TypeError.

Object-Oriented with a difference

Both PHP and JavaScript are object-oriented languages.  While PHP provides the class construct as the basis for creating objects, JavaScript is prototypes based.  Object inheritance in PHP is class-based with the provision for a class to extend one other class. Inheritance in JavaScript is prototypical. The Object data type in JavaScript is at the top of the prototype hierarchy. JavaScript is a highly functional programming language. The equivalent of PHP’s class could be considered to be a special kind of function called constructor functions, which are used to define and initialize objects.

In this article, we discussed the main differences between JavaScript and PHP.