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PHP course · Beginner · Lesson 4/116

Learn to write single-line (//, #) and multi-line (/* */) comments in PHP.

Comments

Comments are used to add explanations to PHP code. PHP ignores comments when running; they do not affect the output.

There are three types: // for single line, # for single line (shell style), and /* */ for multi-line comments.

Example: // this is a note or /* this is also a note */.

Comments make code readable; they are especially useful for explaining complex logic.

Multi-line comments

In PHP, /* */ marks a multi-line comment. This type is ideal for explanations that span several lines.

Example: /* This comment spans two lines */

Multi-line comments cannot be nested: starting another /* */ inside one causes a PHP error.

You can also use multi-line comments to temporarily disable a piece of code.

Exercise Write a comment and echo

Write a PHP block. Add a single-line // comment. Then use echo to print "Welcome back"; add \n at the end of the line.

Show example solution 
Write a // comment, then add echo "Welcome back\n";.
Example solution:
<?php
// greeting message
echo "Welcome back\n";

Test yourself

  1. Which comment starts with the # sign?

    • // comment
    • /* comment */
    • # comment
    • <!-- comment -->
    Show answer

    # comment — Correct! A line starting with # is a comment.

  2. Complete the comment line

    <?php
____
echo "Welcome back";
?>
    Show answer 
    <?php
// greeting message
echo "Welcome back";
?>

  3. Match the comment types

    //
    C-style comment
    #
    Shell-style comment
    /* */
    Multi-line comment

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