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What is PHP?

PHP course · Beginner · Lesson 1/116

Learn that PHP is a server-side language and how it differs from the browser.

What is PHP?

PHP is a server-side programming language. It was designed to make websites dynamic.

When a browser requests a PHP page, the server runs the PHP code and produces HTML. The browser never sees the PHP code; it only displays the resulting HTML.

PHP was created by Rasmus Lerdorf in 1994 and is now a modern language at version 8.3. WordPress, Wikipedia and millions of sites run on PHP.

Where does PHP run?

PHP code runs on the server. You upload a PHP file to the server; when a visitor requests the page, the server executes the code.

The server sends the result to the browser as HTML. When the visitor views the page source, they see HTML tags, not PHP commands.

This makes PHP secure: sensitive data like a database password never reaches the browser.

Test yourself

  1. Which one is a server-side language?

    • CSS
    • PHP
    • HTML
    • XML
    Show answer

    PHP — Correct! PHP runs on the server side.

  2. PHP, browser and HTML

    PHP
    Server
    Browser
    Client
    HTML
    Output

  3. Which can be done with PHP?

    • Animate in the browser
    • Change the CSS layout
    • Process form data
    • Set a button color
    Show answer

    Process form data — Correct! PHP processes form data on the server.

  4. Where does PHP run?

    PHP runs on the ____.
    Show answer 
    PHP runs on the server.

All lessons in Beginner

1 PHP basics

  1. What is PHP?
  2. PHP tags
  3. Output with echo
  4. Comments
  5. phpinfo() and PHP version
  6. Summary - PHP basics

2 Variables

  1. Declaring variables
  2. Variable naming rules
  3. Reassigning variables
  4. Combining variables
  5. Checking variables with isset() and unset()
  6. Summary - Variables

3 Data types

  1. string and int
  2. float and bool
  3. null and empty value
  4. Type checking with gettype()
  5. Detailed output with var_dump()
  6. Summary - Data types

4 Project: Calculator

  1. Project: Calculator
  2. Number input and operator selection
  3. Computing the operation
  4. Handling error cases
  5. Project final - Calculator

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Concatenation and increment
  6. Summary - Operators

6 String basics

  1. Creating strings
  2. Length with strlen()
  3. String concatenation
  4. Variable interpolation in double quotes
  5. Escape sequences
  6. Summary - String basics

7 Conditionals

  1. The if statement
  2. else and elseif
  3. The switch statement
  4. The ternary operator
  5. Comparison pitfalls
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. The do-while loop
  4. The foreach loop
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Project: Shopping cart
  2. Adding products to the cart
  3. Displaying the cart
  4. Computing the total
  5. Project final - Shopping cart

10 Array basics

  1. Creating arrays
  2. Accessing array elements
  3. Element count with count()
  4. Array output with print_r()
  5. Iterating an array
  6. Summary - Array basics

11 Array methods

  1. array_push() and array_pop()
  2. array_shift() and array_unshift()
  3. Merging with array_merge()
  4. Slicing with array_slice()
  5. in_array() and array_search()
  6. Summary - Array methods

12 Associative arrays

  1. Key-value pairs
  2. Accessing keys
  3. array_keys() and array_values()
  4. Key check with isset()
  5. Iterating associative arrays
  6. Summary - Associative arrays

13 Functions

  1. Defining functions
  2. Calling functions
  3. Returning values
  4. Function scope
  5. Returning arrays from functions
  6. Summary - Functions

14 Parameters

  1. Functions with parameters
  2. Default parameter values
  3. Multiple parameters
  4. Typed parameters
  5. Return type declaration
  6. Summary - Parameters

15 Project: To-do list

  1. Project: To-do list
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Project final - To-do list

16 Advanced string methods

  1. Replacing with str_replace()
  2. Slicing with substr()
  3. Searching with strpos()
  4. Splitting with explode()
  5. Joining with implode()
  6. Summary - Advanced string methods

17 Superglobals

  1. What is a superglobal?
  2. Receiving data with $_GET
  3. Receiving data with $_POST
  4. $_SERVER and server info
  5. Everything with $_REQUEST
  6. Summary - Superglobals

18 Forms

  1. Creating HTML forms
  2. Processing form data
  3. Security with htmlspecialchars()
  4. Form validation basics
  5. Showing error messages
  6. Summary - Forms

19 File inclusion

  1. Including files with include
  2. Including files with require
  3. include_once and require_once
  4. __DIR__ and path management
  5. Layout and partial logic
  6. Summary - File inclusion

20 Beginner final

  1. Challenge - Calculator
  2. Challenge - Secure feedback form
  3. Challenge - Array operations
  4. Challenge - Functions and loops
  5. Challenge - Mini CMS