Comments in PHP - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a single-line comment in PHP.

PHP

<?php
[1] This is a comment
echo "Hello World!";
?>

Drag options to blanks, or click blank then click option'

A#

B<!--

C/*

D//

Attempts:

3 left

💡 Hint

Common Mistakes

Using HTML comment tags for PHP comments.

Using block comment start /* for single-line comments.

In PHP, single-line comments can start with //.

2fill in blank

medium

Complete the code to add a single-line comment using an alternative syntax.

PHP

<?php
[1] This is another single-line comment
echo "Hello again!";
?>

Drag options to blanks, or click blank then click option'

A/*

B#

C//

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using SQL comment syntax like -- which is not valid in PHP.

Using block comment start /* for single-line comments.

PHP also supports single-line comments starting with #.

3fill in blank

hard

Fix the error in the code to properly write a multi-line comment in PHP.

PHP

<?php
[1] This is a
multi-line comment */
echo "Done!";
?>

Drag options to blanks, or click blank then click option'

A/*

B//

C#

D<!--

Attempts:

3 left

💡 Hint

Common Mistakes

Using single-line comment syntax for multi-line comments.

Using HTML comment tags which do not work in PHP.

Multi-line comments in PHP start with /* and end with */.

4fill in blank

hard

Fill both blanks to correctly write a multi-line comment in PHP.

PHP

<?php
[1] This is a
multi-line comment [2]
echo "Finished!";
?>

Drag options to blanks, or click blank then click option'

A/*

B//

C*/

D#

Attempts:

3 left

💡 Hint

Common Mistakes

Not closing the multi-line comment.

Using single-line comment syntax for multi-line comments.

Multi-line comments start with /* and end with */ in PHP.

5fill in blank

hard

Fill all three blanks to write a PHP script with different comment styles.

PHP

<?php
[1] This is a single-line comment
[2] This is another single-line comment
[3] This is a multi-line comment start
This is inside the comment
*/
echo "Comments done!";
?>

Drag options to blanks, or click blank then click option'

A//

B#

C/*

D--

Attempts:

3 left

💡 Hint

Common Mistakes

Using SQL comment syntax like -- which is invalid in PHP.

Not closing multi-line comments properly.

PHP supports // and # for single-line comments, and /* ... */ for multi-line comments.

Practice

1. Which of the following is a correct way to write a single-line comment in PHP?

easy

A.

B. // This is a single-line comment

C. /* This is a single-line comment */

D. # This is not a comment

Solution

1. Step 1: Identify single-line comment syntax in PHP

   PHP supports single-line comments using // and #.

2. Step 2: Check each option

   // This is a single-line comment uses // correctly. is HTML comment syntax, not PHP. /* This is a single-line comment */ is multi-line comment syntax. # This is a single-line comment is also valid in PHP, so # This is not a comment is correct as well.

3. Final Answer:

   // This is a single-line comment -> Option B

4. Quick Check:

   Single-line comment = // or # [OK]

Hint: Single-line comments start with // or # in PHP [OK]

Common Mistakes:

• Confusing HTML comments with PHP comments
• Using multi-line comment syntax for single-line comments
• Thinking # is not a valid comment

2. Which of the following is the correct syntax for a multi-line comment in PHP?

easy

A. /* This is a multi-line comment */

B. // This is a multi-line comment

C. # This is a multi-line comment

D.

Solution

1. Step 1: Recall multi-line comment syntax in PHP

   PHP uses /* ... */ to write multi-line comments.

2. Step 2: Evaluate each option

   /* This is a multi-line comment */ correctly uses /* ... */. Options B and C are single-line comment styles. is HTML comment syntax.

3. Final Answer:

   /* This is a multi-line comment */ -> Option A

4. Quick Check:

   Multi-line comment = /* ... */ [OK]

Hint: Multi-line comments use /* at start and */ at end [OK]

Common Mistakes:

• Using // or # for multi-line comments
• Confusing HTML comments with PHP comments
• Forgetting to close multi-line comment with */

3. What will be the output of the following PHP code?

<?php
// echo 'Hello';
echo 'World';
?>

medium

A. HelloWorld

B. No output

C. Hello

D. World

Solution

1. Step 1: Understand the effect of the comment

   The line // echo 'Hello'; is commented out, so it does not run.

2. Step 2: Identify the executed code

   The line echo 'World'; runs and prints "World".

3. Final Answer:

   World -> Option D

4. Quick Check:

   Commented out code does not run, so output = World [OK]

Hint: Code after // is ignored, only uncommented code runs [OK]

Common Mistakes:

• Thinking commented code runs
• Confusing output by combining commented and uncommented lines
• Ignoring that echo prints text

4. Find the error in the following PHP code:

<?php
/* This is a comment
 echo 'Hello';
// Missing closing tag
?>

medium

A. PHP tags are incorrect

B. Using // inside multi-line comment is invalid

C. Missing closing */ for multi-line comment

D. echo statement syntax error

Solution

1. Step 1: Check multi-line comment syntax

   The multi-line comment starts with /* but never ends with */.

2. Step 2: Understand consequences of missing closing comment

   Without closing */, PHP treats the rest as comment, causing syntax errors or unexpected behavior.

3. Final Answer:

   Missing closing */ for multi-line comment -> Option C

4. Quick Check:

   Multi-line comments must close with */ [OK]

Hint: Always close multi-line comments with */ [OK]

Common Mistakes:

• Forgetting to close multi-line comments
• Thinking // cannot be inside multi-line comments
• Misreading PHP tags as error

5. You want to temporarily disable a block of code without deleting it. Which comment style should you use in PHP to do this safely for multiple lines?

hard

A. Use /* at start and */ at end of the block

B. Use # at the start of the block

C. // Comment each line with //

D. Wrap the block with

Solution

1. Step 1: Understand commenting multiple lines

   Using /* ... */ allows commenting multiple lines at once safely.

2. Step 2: Evaluate other options

   // Comment each line with // requires adding // on each line, which is tedious. Use # at the start of the block is invalid for multiple lines. Wrap the block with is HTML comment syntax, not PHP.

3. Final Answer:

   Use /* at start and */ at end of the block -> Option A

4. Quick Check:

   Multi-line comments use /* ... */ [OK]

Hint: Use /* ... */ to comment multiple lines quickly [OK]

Common Mistakes:

• Using # or // for many lines without repeating
• Confusing HTML comments with PHP comments
• Not closing multi-line comments properly