How to Compare PHP vs JavaScript Learning What Can PHP Do That JavaScript Can't

In this article you will learn:

1. All Programming Languages Are Pretty General-Purpose

2. Both JavaScript and PHP Can Run Server-Side

3. Both JavaScript and PHP Are Object-Oriented and Have Extensive Support for Inheritance and Polymorphism

What Can PHP Do That JavaScript Can't

This is a bit like asking what you can say in German that you wouldn't know in English. In general, there is very little you can't do with programming language X that you strictly cannot do with programming language Y. 

1. All Programming Languages Are Pretty General-Purpose

Deciding which language is best is more about what one language is more suited to do.

There are syntactical differences in how you do things in one language but cannot do in the other.

For example, PHP has variable variables, JavaScript has closures, and German has the excellent word Schadenfreude. But that's generally just different ways of approaching things.

Also, I want to clarify some things because I feel there is a bit of misinformation in other answers.

2. Both JavaScript and PHP Can Run Server-Side

Web browsers have JavaScript engines built in, which makes many people assume that JavaScript is for clients and PHP is for servers. This is false.

JavaScript is widely used in production server-side, using node.js. Node.js is not another language, it's just JavaScript. Simple, low-cost options are available for small deployments, and large companies like PayPal use them in production.

3. Both JavaScript and PHP Are Object-Oriented and Have Extensive Support for Inheritance and Polymorphism

PHP is more classically oriented, and you will be more comfortable with it if you come from a Java background. At the same time, JavaScript has a more flexible (but harder to understand) inheritance model called prototypal inheritance.

Both JavaScript and PHP have classes, but PHP has more extensive support.

You tend not to need classes as much in JavaScript for several reasons, but that's beyond the scope of this answer.

4. Both JavaScript and PHP Have Extremely Cheap Hosting Options Available on the Market

For initial small-scale deployments, both have very cheap or free options available.

When you move to VPS or, more significantly, they both have similar performance requirements.