PHP Basics: Variables and Math Operations

Storing Numbers in Variables

• Creating Variables

  • Example: $number = 10;

• Printing Variables

  • Use echo to display the value: echo $number; outputs 10.

Performing Operations with Variables

• Addition of Variables

  • Example:

    $anotherNumber = 5;
    echo $number + $anotherNumber; // Outputs 15

• Incrementing and Decrementing

  • Increment: $number++; (Increases value by 1)

  • Decrement: $number--; (Decreases value by 1)

Arithmetic Operations

• Shorthand Operations

  • Addition: num += 25; (Equivalent to num = num + 25;)

  • Other operations: num -= 25;, num *= 25;, num /= 25;

Advanced Math Functions in PHP

• Using Built-in Functions

  • Absolute Value: abs(-100); returns 100.

  • Power: pow(2, 4); returns 16.

  • Square Root: sqrt(144); returns 12.

  • Maximum and Minimum:

    • max(2, 10); returns 10.

    • min(2, 10); returns 2.

  • Rounding Functions:

    • round(2.5); returns 3.

    • ceil(3.3); returns 4.

    • floor(3.9); returns 3.

User Input in PHP

• Setting Up Forms

  • Forms allow user interaction and data submission.

  • Basic HTML form structure:

    <form action="site.php" method="POST">
      <input type="text" name="student">
      <input type="submit" value="Submit">
    </form>

• Accessing User Input

  • Use $_POST to retrieve submitted data:

    echo grades[$_POST['student']];

Associative Arrays in PHP

Introduction to Associative Arrays

• Key-Value Pairs

  • Store data in pairs, e.g., student names and grades.

  • Example:

    $grades = array("Jim" => "A+", "Pam" => "B-", "Oscar" => "C+");

Accessing Associative Array Elements

• Using Keys to Access Values

  • Example: echo $grades["Jim"]; outputs A+.

Modifying Associative Arrays

• Updating Values

  • Example: $grades["Jim"] = "F"; changes Jim's grade.

Functions in PHP

Introduction to Functions

• Purpose of Functions

  • Group related code for specific tasks.

  • Example of a simple function:

    function sayHi() {
        echo "Hi!";
    }

Creating and Using Functions

• Defining a Function

  • Use the function keyword.

• Calling a Function

  • Simply use the function name followed by parentheses.

Constructors in PHP

Understanding Constructors

• Purpose of Constructors

  • Automatically initialize object properties when an object is created.

• Defining a Constructor

  • Use the __construct method:

    function __construct($title, $author, $pages) {
        $this->title = $title;
        $this->author = $author;
        $this->pages = $pages;
    }

Creating Objects with Constructors

• Example of Object Creation

  • Create a new book object:

    $book1 = new Book("Harry Potter", "JK Rowling", 400);

Benefits of Using Constructors

• Simplifies Object Creation

  • Reduces lines of code and potential errors.

• Example of Accessing Object Properties

  • echo $book1->title; outputs Harry Potter.

Summary

• Understanding variables, math operations, user input, associative arrays, functions, and constructors is crucial for effective PHP programming.

• These concepts form the foundation for building dynamic and interactive web applications.