Hello World in PHP

Every programming journey starts with Hello World. Let’s write our first PHP program.

The Code

Create a file named hello.php:

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<?php
echo "Hello, World!\n";

Understanding the Code

• <?php - The opening tag that tells the server to interpret what follows as PHP code.
• echo - A language construct that outputs one or more strings. It’s the most common way to output text in PHP.
• "Hello, World!\n" - A string literal with a newline character at the end.
• No closing tag - When a file contains only PHP code, it’s best practice to omit the closing ?> tag to avoid accidental whitespace issues.

Running with Docker

The easiest way to run this without installing PHP locally:

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# Pull the official PHP CLI image
docker pull php:8.3-cli-alpine

# Run the program
docker run --rm -v $(pwd):/app -w /app php:8.3-cli-alpine php hello.php

Running Locally

If you have PHP installed:

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php hello.php

Expected Output

Hello, World!

Alternative Syntax

PHP offers several ways to output text:

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<?php
// Using echo (most common)
echo "Hello, World!\n";

// Using print (similar to echo, but returns 1)
print "Hello, World!\n";

// Short echo syntax (useful in templates)
// Note: Requires short_open_tag or always works with <?=
?>
<?= "Hello, World!\n" ?>

Key Concepts

1. PHP is interpreted - Code is executed line by line by the PHP interpreter
2. Designed for the web - PHP was created specifically for web development
3. Embedded in HTML - PHP can be mixed with HTML in .php files
4. Flexible typing - Variables don’t require type declarations (though type hints are available in modern PHP)

PHP Tags

PHP code must be enclosed in tags:

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<?php
// Full opening tag - always works
echo "Hello";
?>

For files containing only PHP code (like libraries), omit the closing tag:

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<?php
// No closing tag needed - prevents whitespace issues
echo "Hello, World!\n";

Next Steps

Continue to Variables and Data Types to learn about storing and manipulating data in PHP.