PHP Introduction

PHP (Hypertext Preprocessor) is a popular server-side scripting language designed for web development but also used as a general-purpose language. It’s especially known for its role in creating dynamic web pages and web applications.

Basic PHP Syntax

PHP code is embedded in HTML using the <?php ... ?> tags. Here’s a simple example:

<!DOCTYPE html>
<html>
<head>
    <title>PHP Example</title>
</head>
<body>
    <?php
        echo "Hello, World!";
    ?>
</body>
</html>

Output:

When this PHP code is executed on a server, it generates the following HTML:

<!DOCTYPE html>
<html>
<head>
    <title>PHP Example</title>
</head>
<body>
    Hello, World!
</body>
</html>

Variables

PHP variables start with the $ symbol. Variables do not require explicit declaration and are loosely typed.

<?php
    $greeting = "Hello, ";
    $name = "Alice";
    echo $greeting . $name;
?>

Output:

Hello, Alice

Control Structures

PHP supports standard control structures such as if, else, while, for, and foreach.

Example with if statement:

<?php
    $age = 18;
    
    if ($age >= 18) {
        echo "You are an adult.";
    } else {
        echo "You are not an adult.";
    }
?>

Output:

You are an adult.

Functions

Functions in PHP are defined using the function keyword.

Example:

<?php
    function greet($name) {
        return "Hello, " . $name;
    }

    echo greet("Bob");
?>

Output:

Hello, Bob

Arrays

PHP supports both indexed and associative arrays.

Indexed Array Example:

<?php
    $fruits = array("Apple", "Banana", "Cherry");
    echo $fruits[1];  // Outputs: Banana
?>

Associative Array Example:

<?php
    $person = array("first_name" => "John", "last_name" => "Doe");
    echo $person["first_name"];  // Outputs: John
?>

Connecting to a Database

PHP is often used with MySQL databases. Here’s a simple example of connecting to a MySQL database and querying it:

<?php
    $servername = "localhost";
    $username = "username";
    $password = "password";
    $dbname = "my_database";

    // Create connection
    $conn = new mysqli($servername, $username, $password, $dbname);

    // Check connection
    if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
    }
    echo "Connected successfully";

    // Perform a query
    $sql = "SELECT id, name FROM users";
    $result = $conn->query($sql);

    if ($result->num_rows > 0) {
        // Output data of each row
        while($row = $result->fetch_assoc()) {
            echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
        }
    } else {
        echo "0 results";
    }

    $conn->close();
?>

Output:

Connected successfully
id: 1 - Name: Alice
id: 2 - Name: Bob
...

These examples provide a glimpse into PHP’s capabilities, from basic syntax and variables to functions and database interactions.

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