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StreetGeek Academy · PHP Foundations

🧩 Module 2: PHP Syntax and Basic Concepts

Objective: Learn the foundational syntax and data handling structures of PHP — including variables,
data types, constants, and debugging functions.

🔹 1. PHP Tags and Comments

Every PHP file starts and ends with PHP tags:

<?php
    // Your code goes here
?>

These tags tell the server where PHP code begins and ends. Anything outside them is treated as plain HTML.

💬 Comments

Comments let you explain your code and are ignored by PHP when running.

<?php
// Single-line comment
# Also a single-line comment
/*
   Multi-line
   comment
*/
?>

🧠 Best practice: Use comments to describe what your code does — especially when defining functions or logic.

🔹 2. Variables

Variables in PHP store data. They always start with a $ sign and are case-sensitive. 

<?php
$name = "Yogi";
$age = 30;
echo $name; // Outputs: Yogi
?>

🧩 Naming Rules:

  • Must start with $
  • Must begin with a letter or underscore
  • Cannot contain spaces or start with a number
  • Are case-sensitive ($name ≠ $Name)

🔹 3. Data Types

PHP automatically determines a variable’s type based on its value. The main data types are:

Type Example Description
String "Hello, StreetGeek" Text data
Integer 25 Whole number
Float / Double 3.14 Decimal number
Boolean true or false Logical value
Array [1, 2, 3] or array("red", "blue") Multiple values
NULL NULL Empty or undefined variable
Object new ClassName() Instance of a class

🔹 4. Constants

Constants are like variables — but their values cannot change once defined. 

<?php
define("SITE_NAME", "StreetGeek Academy");
echo SITE_NAME;
?>

You can also use:

const VERSION = "1.0";

🔹 5. String Concatenation & Interpolation

🧩 Concatenation

Join strings using a dot (.):

$name = "Yogi";
echo "Hello " . $name . "!";

🧩 Interpolation

If you use double quotes, variables are automatically inserted into strings:

$name = "Yogi";
echo "Hello $name!";

Single quotes (' ') do not parse variables:

echo 'Hello $name!'; // Outputs literally: Hello $name!

🔹 6. Debugging with var_dump()

Debugging means understanding what data your variables actually hold.

$city = "Richmond";
var_dump($city);

Output example:

string(8) "Richmond"

You can also inspect multiple values:

$name = "Yogi";
$age = 30;
$is_student = true;

var_dump($name, $age, $is_student);

🧩 Hands-On Practice

Exercise 1: Variables and Strings

Create a new file named variables.php in your php-basics folder and add:

<?php
$name = "Yogi";
$language = "PHP";
echo "Hello $name, welcome to $language programming!";
?>

✅ Output should be:

Hello Yogi, welcome to PHP programming!

Exercise 2: Data Type Practice

Add this code below your first example:

<?php
$name = "StreetGeek Academy";
$students = 100;
$rating = 4.9;
$is_open = true;
$launch_year = NULL;

var_dump($name, $students, $rating, $is_open, $launch_year);
?>

✅ Check the output — PHP tells you the data type and value of each variable.

Exercise 3: Constants and Concatenation

Create a file named constants.php:

<?php
define("ACADEMY", "StreetGeek Academy");
const FOUNDED = 2025;

echo "Welcome to " . ACADEMY . "!";
echo "<br>";
echo "Established in " . FOUNDED . ".";
?>

✅ Output:

Welcome to StreetGeek Academy!
Established in 2025.

Exercise 4: Debug Challenge

Create a script debug.php with these lines:

<?php
$students = "50";
$enrolled = 50;
if ($students === $enrolled) {
    echo "They are equal.";
} else {
    echo "They are not equal.";
}
?>

✅ What happens?
=== checks for both value and type, so "50" (string) ≠ 50 (integer).
🧠 Takeaway: Always be aware of your variable types!

📝 Module 2 Quiz

# Question Options Correct
1 What symbol must all variables begin with? a) # · b) $ · c) % b
2 Which function displays data type and value? a) print() · b) var_dump() · c) inspect() b
3 How do you define a constant? a) set(“PI”, 3.14) · b) const PI = 3.14 · c) define(“PI”, 3.14) c
4 What is the result of 'Hello $name' if $name = "Yogi"? a) Hello Yogi · b) Hello $name · c) Error b
5 What is the difference between == and ===? a) None · b) == compares values, === compares values and types b

💪 Challenge Task – Personal Bio Page

Objective: Create a PHP page that introduces yourself using variables, constants, and HTML.

  1. Create a new file bio.php inside your php-basics folder.
  2. Add variables for your:
    • Name
    • Age
    • Favorite language
    • Hobby
  3. Create a constant called ACADEMY = "StreetGeek Academy".
  4. Output a small HTML profile page like this:
<!DOCTYPE html>
<html>
<head><title>About Me</title></head>
<body>
<h1>Welcome to <?php echo ACADEMY; ?></h1>
<p>My name is <?php echo $name; ?>.</p>
<p>I’m <?php echo $age; ?> years old and I love coding in <?php echo $language; ?>.</p>
<p>My favorite hobby is <?php echo $hobby; ?>.</p>
</body>
</html>

✅ Bonus: Use var_dump() to check the data types of your variables at the end of the page.

🧾 Submission Checklist

  • ✅ variables.php → shows personalized message
  • ✅ constants.php → uses both define() and const
  • ✅ debug.php → demonstrates strict comparison
  • ✅ bio.php → personal info using variables + constants
  • ✅ Quiz completed

🏁 Next Step: In Module 3, you’ll use what you’ve learned here to perform calculations and logic with PHP —
mastering operators and expressions to build functional scripts like a discount calculator.