PHP block commenting is essential for documenting logic, disabling code, and creating structured docblocks; 1. Use / / for multi-line comments but avoid nesting, as it causes parse errors; 2. You can safely include // comments inside / / blocks; 3. Always close block comments with / to prevent unintended code exclusion; 4. Use / / DocBlocks for public APIs to enable IDE support and tooling integration with @param, @return, and @throws annotations; 5. Keep comments meaningful, update outdated ones, explain intent over mechanics, and avoid leaving large commented-out code sections in production—use version control instead; proper block commenting enhances readability, maintainability, and team collaboration, making it a vital practice in professional PHP development.

PHP block commenting might seem straightforward, but mastering its nuances can significantly improve code readability, maintainability, and collaboration—especially in larger projects. While // and # handle single-line comments, block comments using /* ... */ serve a different purpose: documenting logic, temporarily disabling code sections, or writing structured docblocks for tools like PHPDoc. Let’s break down the practical and often overlooked aspects of PHP block commenting.

When and Why to Use Block Comments

Block comments are ideal when you need to:

• Comment out multiple lines of code during debugging.
• Write detailed explanations for complex logic.
• Create structured documentation using PHPDoc standards.
• Preserve temporary notes that span several lines.

Unlike single-line comments, block comments don’t require prefixing each line with //, making them cleaner for longer annotations.

/*
This function calculates compound interest
but only applies it to verified accounts.
Pending further review with the finance team.
*/
function calculateInterest($principal, $rate, $time) {
    // ... logic here
}

?? Note: Avoid using /* */ inside expressions or strings—it can break syntax if nested or improperly closed.

Proper Syntax and Common Pitfalls

The basic syntax is simple:

/*
This is a valid
multi-line comment
*/

But there are traps:

1. No Nesting

You cannot nest /* */ comments. This will cause a parse error:

/*
    /*
     This breaks!
    */
*/

Instead, use single-line comments within block comments if needed, or refactor.

2. Use // Inside /* */? Yes!

Even within a /* */ block, you can include // without issue:

/*
Planning to refactor:
// Old method: calculateLegacyRate()
// Now using: calculateRevisedRate()
Will update after testing.
*/

This is safe because // is ignored once inside the block.

3. *Don’t Forget the Closing `/`**

An unclosed block comment will comment out everything until the next */—possibly hundreds of lines down. This can lead to mysterious "disappearing" code.

Using Block Comments for PHPDoc (DocBlocks)

One of the most powerful uses of block comments is writing DocBlocks—structured comments that document classes, methods, and properties. These are parsed by IDEs and tools like PHPStan or Laminas Code.

/**
 * Represents a user in the system.
 *
 * @package App\Models
 * @author  Jane Doe <jane@example.com>
 */
class User
{
    /**
     * Calculate monthly subscription cost.
     *
     * @param int $months Number of months to bill
     * @param bool $isPremium Whether user has premium access
     * @return float Total cost after discount
     * @throws InvalidArgumentException If months is less than 1
     */
    public function getSubscriptionCost($months, $isPremium)
    {
        if ($months < 1) {
            throw new InvalidArgumentException("Months must be at least 1.");
        }
        // ... logic
    }
}

Key points:

• Start with /** (two asterisks) for DocBlocks.
• Use @param, @return, @throws, etc., for clarity.
• IDEs use this to provide auto-completion and type hints.

Best Practices for Clean, Useful Block Comments

• Be concise but meaningful. Avoid obvious statements like /* start loop */.
• Update or remove outdated comments. A stale comment is worse than no comment.
• Use block comments for intent, not just mechanics. Explain why, not what.
• Prefer DocBlocks for public APIs. They integrate well with tooling.
• Avoid large commented-out code blocks in production. Use version control instead.

? Tip: If you’re commenting out code for more than a few hours, commit it to a feature branch. Leaving dead code in files confuses teammates.

Basically, PHP block commenting is more than just hiding code—it's a tool for communication. Whether you're documenting a complex algorithm or writing machine-readable PHPDoc, getting the details right helps everyone (including future you). Just remember: no nesting, always close, and keep it relevant.

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