Understanding Comments in PHP

Like any other programming languages, PHP supports different types of comments. Though comments are ignored by the PHP interpreter, they are essential for developer experience (DX). Let’s learn more about comments in PHP.

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Types of Comments in PHP

PHP supports three types of comments:

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1. Single Line Comments

Single-line comments are used to comment out a single line or part of a line in your code. You can use either // or # to denote a single-line comment.

Example:

<?php
// This is a single-line comment using double slashes.

echo "Hello, World!"; // This comment is at the end of a line.

# This is another way to write a single-line comment using a hash.
?>

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2. Multi-line Comments

Multi-line comments, also known as block comments, are used to comment out multiple lines of code. They start with /* and end with */. This type of comment is useful when you need to temporarily disable large blocks of code or write longer explanations.

Example:

<?php
/* 
   This is a multi-line comment.
   It can span multiple lines.
   It is useful for commenting out large sections of code.
*/
echo "This line will be executed.";

?>

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3. Documentation Comments

Documentation comments are a specialized form of multi-line comments. They start with /** and are often used to generate documentation using tools like PHPDoc. This type of comment is typically placed above functions, classes, or methods to describe their purpose, parameters, and return values.

Example:

<?php
/**
 * Adds two numbers together.
 *
 * @param int $a The first number.
 * @param int $b The second number.
 * @return int The sum of the two numbers.
 */
function add($a, $b) {
    return $a + $b;
}

echo add(3, 4); // Outputs: 7
?>

The @param and @return annotations provide metadata that can be used by documentation generators to produce well-structured and detailed documentation.

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Best Practices for Using Comments

1. Keep Comments Relevant and Up-to-Date: Outdated comments can be more confusing than no comments at all. Always update your comments when you change the code.
2. Avoid Obvious Comments: Comments like // Increment by 1 above a line of code like $i++; are unnecessary. Comments should add value by explaining why the code does something, not what it does.
3. Use Documentation Comments for Functions and Classes: This helps you and others understand what the function or class does, what parameters it accepts, and what it returns.
4. Use Comments to Explain Complex Logic: If your code contains complex logic or algorithms, use comments to break it down and explain the reasoning behind your approach.

<?php

//======================================================================
// CATEGORY LARGE FONT
//======================================================================

//-----------------------------------------------------
// Sub-Category Smaller Font
//-----------------------------------------------------

/* Title Here Notice the First Letters are Capitalized */

# Option 1
# Option 2
# Option 3

/*
 * This is a detailed explanation
 * of something that should require
 * several paragraphs of information.
 */

// This is a single line quote.
?>