Lab 01: Hello World & PHP Basics

🎯 Objective

Learn to write your first PHP program, understand PHP syntax, use echo for output, and work with variables.

📚 Background

PHP (Hypertext Preprocessor) is a widely-used server-side scripting language. PHP code is embedded within <?php and ?> tags. Variables start with $ and are dynamically typed, meaning you don't need to declare their type upfront.

⏱️ Estimated Time

20 minutes

📋 Prerequisites

• Basic understanding of programming concepts

• Docker installed and innozverse-php:latest image available

🛠️ Tools Used

• PHP 8.3 CLI

• Docker (innozverse-php:latest)

---

🔬 Lab Instructions

Step 1: Your First PHP Script

Create a file /tmp/lab01.php:

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

Run it:

docker run --rm -v /tmp:/tmp innozverse-php:latest php /tmp/lab01.php

📸 Verified Output:

Hello, World!

💡 echo outputs text to the screen. The \n is a newline character.

---

Step 2: Variables

<?php
$name = "PHP";
$version = 8.3;
$year = 2025;

echo "Language: $name\n";
echo "Version: $version\n";
echo "Year: $year\n";

📸 Verified Output:

Language: PHP
Version: 8.3
Year: 2025

💡 Variables are prefixed with $. PHP is loosely typed — no type declaration needed.

---

Step 3: Variable Types and var_dump

<?php
$str    = "Hello";
$int    = 42;
$float  = 3.14;
$bool   = true;
$null   = null;

var_dump($str);
var_dump($int);
var_dump($float);
var_dump($bool);
var_dump($null);

📸 Verified Output:

string(5) "Hello"
int(42)
float(3.14)
bool(true)
NULL

💡 var_dump() shows both the type and value — great for debugging.

---

Step 4: String Concatenation

<?php
$first = "Hello";
$last  = "World";

// Method 1: concatenation with .
$full = $first . ", " . $last . "!";
echo $full . "\n";

// Method 2: string interpolation
echo "$first, $last!\n";

// Method 3: complex expressions in strings
$count = 5;
echo "There are {$count} items\n";

📸 Verified Output:

Hello, World!
Hello, World!
There are 5 items

---

Step 5: Constants

<?php
define("APP_NAME", "InnoZverse");
define("MAX_USERS", 1000);

const VERSION = "1.0.0";

echo APP_NAME . "\n";
echo MAX_USERS . "\n";
echo VERSION . "\n";

📸 Verified Output:

InnoZverse
1000
1.0.0

💡 Constants don't use $ and cannot be changed after definition.

---

Step 6: PHP Comments

<?php
// Single-line comment

# Also a single-line comment

/*
 * Multi-line comment
 * Useful for documentation
 */

$x = 10; // Inline comment

echo $x . "\n";

/**
 * PHPDoc comment — used for documentation
 * @param string $name
 * @return string
 */
function greet(string $name): string {
    return "Hello, $name!";
}

echo greet("Developer") . "\n";

📸 Verified Output:

10
Hello, Developer!

---

Step 7: Print and Printf

<?php
print("Using print\n");  // print is similar to echo but returns 1

$price  = 9.99;
$qty    = 3;
$total  = $price * $qty;

printf("Price: $%.2f x %d = $%.2f\n", $price, $qty, $total);

// sprintf returns a string
$msg = sprintf("Total cost: $%05.2f", $total);
echo $msg . "\n";

📸 Verified Output:

Using print
Price: $9.99 x 3 = $29.97
Total cost: $29.97

---

Step 8: A Complete Mini Program

<?php
$name    = "Alice";
$age     = 30;
$city    = "New York";
$salary  = 75000.50;

echo "=== User Profile ===\n";
echo "Name:   $name\n";
echo "Age:    $age years\n";
echo "City:   $city\n";
printf("Salary: $%,.2f\n", $salary);
echo "Adult:  " . ($age >= 18 ? "Yes" : "No") . "\n";
echo "Born:   " . (date("Y") - $age) . "\n";

📸 Verified Output:

=== User Profile ===
Name:   Alice
Age:    30 years
City:   New York
Salary: $75,000.50
Adult:  Yes
Born:   1996

---

✅ Verification

Run all snippets through Docker successfully. Confirm:

• echo outputs text

• Variables hold different types

• String interpolation works with "$var" and "{$var}"

• Constants are defined with define() or const

🚨 Common Mistakes

Mistake	Fix
Forgetting $ on variables	Always prefix variables with $
Using single quotes for interpolation	Use double quotes: "Hello $name"
Missing semicolons	Every statement must end with ;
<? without php	Use full <?php opening tag

📝 Summary

• PHP scripts begin with <?php

• Variables start with $ and are dynamically typed

• Use echo or print for output

• String interpolation works in double-quoted strings

• var_dump() shows type and value

• Constants use define() or const

🔗 Further Reading

• PHP Manual: Basic Syntax

• PHP Variables

• PHP echo