PHP Comments

What Are PHP Comments?

A comment in PHP is a piece of text inside your code that:

✅ Is ignored by the PHP interpreter

✅ Does NOT run as part of the program

✅ Is only there for humans to read

Think of comments as notes for yourself or other developers.

Simple Example

<?php
// This is a comment
echo "Hello world!";
?>

Output:

Hello world!

The comment is not displayed because PHP ignores it.

Why Comments Are Important

Comments help you:

• Explain what your code is doing
• Make your code easier to understand
• Debug problems
• Work with other developers
• Remember your logic in the future

Without comments, code can look confusing very fast.

Types of PHP Comments

PHP has three main types.

1️⃣ Single-line Comment (//)

Used for short explanations.

// This is a single-line comment
echo "Welcome";

2️⃣ Single-line Comment (#)

Works like // but less commonly used.

# This is also a single-line comment
echo "Hello";

3️⃣ Multi-line Comment (/* */)

Used for longer notes or disabling blocks of code.

/*
This is a multi-line comment
It can span multiple lines
*/
echo "PHP is fun!";

PHP Comment Types

| Comment Type        | Symbol Used | Purpose                          | Example                     |
|---------------------|------------|----------------------------------|-----------------------------|
| Single-line comment | //         | Short explanation                | // This is a comment        |
| Single-line comment | #          | Alternative single-line comment  | # This is a comment         |
| Multi-line comment  | /* */      | Long explanations or code blocks | /* multi-line comment */    |

Example

Without Comments

<?php
$u = "Danny";
echo $u;
?>

You may forget what $u means later.

With Comments

<?php
// Store the username
$username = "Danny";

// Display the username
echo $username;
?>

Now the code is clear and readable.

Using Comments to Disable Code

This is useful for testing.

<?php
echo "This will show";

// echo "This will NOT show";
?>

Or:

<?php
/*
echo "Line 1";
echo "Line 2";
*/
echo "Only this runs";
?>

Where Comments Are Commonly Used

1. Explaining Variables

// Database connection name
$db_name = "my_database";

2. Explaining Functions

// This function calculates total price
function total($price, $qty) {
    return $price * $qty;
}

3. Section Headers

// =======================
// USER LOGIN SECTION
// =======================

Beginner vs Clean Code

❌ Bad Comment

// add 1 to i
$i = $i + 1;

This is obvious — no need to comment.

✅ Good Comment

// Increase login attempt count for security check
$login_attempts++;

This explains why, not just what.

Best Practices for PHP Comments

✔ Write comments for complex logic

✔ Keep them short and clear

✔ Update comments when code changes

✔ Explain WHY something is done

Common Mistakes

1. Too Many Comments

// create variable
$name = "John";

Not needed.

2. Outdated Comments

// This stores email
$username = "Danny";

This creates confusion.

3. Commenting Every Line

Makes code messy.

Documentation-Style Comments

Used for professional projects:

/**
 * This function registers a new user
 *
 * @param string $username
 * @param string $password
 * @return bool
 */
function registerUser($username, $password) {
    return true;
}

These are used by tools and IDEs.