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Introduction to PHP

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Comments in PHP

Usage of Comments

Developers often need tools to make their code easier to understand, both for themselves and for the people they work with. Comments are one such tool, as they allow us to explain parts of the code. The PHP interpreter ignores comments, so they don't affect the execution of the program. Comments can be used for:

1. Explaining what the code does:

php

index

copy
<?php
echo "Correct"; // Output the word 'Correct' to the console
?>

              
123

            
<?php
echo "Correct"; // Output the word 'Correct' to the console
?>

The comment above clearly indicates to us what exactly this code does.

2. Commenting out code blocks to avoid errors at runtime:

php

main

copy
<?php
echo "Hello, World!";
// echo "Hello, World!"; // This line is commented out and won't execute
echo "Hello, World!";
?>

              
12345

            
<?php
echo "Hello, World!";
// echo "Hello, World!"; // This line is commented out and won't execute
echo "Hello, World!";
?>

The comment above clearly demonstrates that the commented lines of code are ignored and do not affect the code execution result.

Single-Line and Multi-Line Comments

A single-line comment starts with // and continues to the end of the line:

php

main

copy
<?php
echo "info"; // Output "info" to the console
?>

              
123

            
<?php
echo "info"; // Output "info" to the console
?>

A multi-line comment starts with /* and ends with */. It can span multiple lines:

php

main

copy
<?php
/*
This is a multi-line
comment.
*/
echo "Very useful topic";
?>

              
1234567

            
<?php
/*
This is a multi-line
comment.
*/
echo "Very useful topic";
?>
question mark

How many times will the word "Hello, World!" be displayed in the console?

<?php
// echo "Hello, World!";
echo "Hello, World!";
/*
echo "Hello, World!"
*/
echo "Hello, World!";
?>

Select the correct answer

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