PHP Syntax and Backend Basics

# CHAPTER 4

PHP Syntax and Backend Basics #

1. Introduction #

2. Learning Objectives #

• Write basic PHP syntax and use the echo statement.

• Declare variables and understand basic data types.

• Write conditional logic using if/else statements.

• Use for and while loops to process repetitive tasks.

3. Beginner-Friendly Explanation #

4. Basic Syntax and Echo #

<?php
// This is a single-line comment. The server ignores this.

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

echo "<h1>Welcome to my App</h1>";
echo "This is standard text.";
?>

5. Variables and Data Types #

<?php
$name = "John Doe";      // String (Text)
$age = 30;               // Integer (Whole number)
$price = 19.99;          // Float (Decimal)
$is_admin = true;        // Boolean (True/False)

// Concatenation: Joining text and variables using a dot (.)
echo "My name is " . $name . " and I am " . $age . " years old.";
?>

6. Conditional Logic (If / Else) #

<?php
$user_role = "admin";
$account_balance = 50;

// Basic If/Else
if ($user_role == "admin") {
    echo "Welcome to the Admin Dashboard.";
} else {
    echo "Welcome to the User Profile.";
}

// Complex Conditions (&& means AND, || means OR)
if ($account_balance < 100 && $user_role != "admin") {
    echo "Low balance warning.";
}
?>

7. Loops (Automating Tasks) #

<?php
// A 'For' Loop: runs exactly 5 times
echo "<ul>";
for ($i = 1; $i <= 5; $i++) {
    echo "<li>Item Number: " . $i . "</li>";
}
echo "</ul>";

// A 'While' Loop: runs as long as the condition is true
$inventory = 3;
while ($inventory > 0) {
    echo "<p>Selling an item. Items left: " . $inventory . "</p>";
    $inventory--; // Subtract 1 from inventory
}
echo "<p>Sold out!</p>";
?>

8. Backend Workflow Example: A Simple Paywall #

<?php
$has_subscription = false;
$article_preview = "The stock market crashed today due to...";
$full_article = "The stock market crashed today due to rising interest rates and inflation.";

echo "<h2>Financial News Daily</h2>";

if ($has_subscription) {
    echo "<p>" . $full_article . "</p>";
} else {
    echo "<p>" . $article_preview . " <b>[Read More...]</b></p>";
    echo "<a href=&#039;subscribe.php'><button>Subscribe to Read Full Article</button></a>";
}
?>

9. Best Practices #

• Naming Conventions: Use clear, descriptive variable names. Use camelCase ($userAge) or snake_case ($user_age), but pick one and stay consistent throughout your entire application.

10. Common Mistakes #

• The Missing Semicolon: The #1 error beginners face is a completely broken page resulting from a "Syntax Error" or "Parse Error." 99% of the time, it is because you forgot to put a semicolon ; at the end of the previous line of code.

11. Exercises #

1. 1. Write a PHP script with a variable $temperature. Write an if/else if/else block that prints "It's freezing!" if below 32, "It's nice!" if between 32 and 80, and "It's hot!" if above 80.

12. Coding Challenges #

• Challenge: Write a for loop that prints the multiplication table of 7 (e.g., "7 x 1 = 7", "7 x 2 = 14", all the way up to 10).

13. MCQs with Answers #

14. Interview Questions #

• Q: Explain the difference between == and === in PHP conditional statements.

• Q: Describe a scenario in a web application where a while loop would be more appropriate than a for loop.

15. FAQs #

16. Summary #

17. Next Chapter Recommendation #