Welcome to PHP

PHP is a server-side scripting language used to build dynamic websites and web applications.

<?php
echo "Hello, PHP!";
?>
    

You can install PHP using XAMPP, WAMP, or install it directly from php.net.

# Check PHP version
php -v
    

Variables in PHP start with a $ sign and store data.

<?php
$name = "Zohil";
$age = 20;

echo $name;
?>
    

PHP supports multiple data types like string, integer, float, boolean, and arrays.

<?php
$name = "Ali";     // String
$age = 25;        // Integer
$price = 10.5;    // Float
$isStudent = true; // Boolean
?>
    

Operators are used to perform operations like addition, comparison, etc.

<?php
$a = 5;
$b = 3;

echo $a + $b; // 8
echo $a > $b; // true
?>
    

The if statement is used to execute code based on a condition.

<?php
$age = 18;

if ($age >= 18) {
  echo "You are an adult";
}
?>
    

If-else allows you to handle two possible outcomes.

<?php
$age = 16;

if ($age >= 18) {
  echo "Adult";
} else {
  echo "Minor";
}
?>
    

Switch is used to select one option from multiple cases.

<?php
$day = "Monday";

switch ($day) {
  case "Monday":
    echo "Start of week";
    break;
  default:
    echo "Other day";
}
?>
    

The for loop repeats code a specific number of times.

<?php
for ($i = 1; $i <= 5; $i++) {
  echo $i;
}
?>
    

The while loop runs as long as the condition is true.

<?php
$i = 1;

while ($i <= 5) {
  echo $i;
  $i++;
}
?>
    

Functions allow you to reuse code by defining it once and calling it multiple times.

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

echo greet("Zohil");
?>
    

Arrays store multiple values in a single variable.

<?php
$fruits = ["Apple", "Banana", "Orange"];
echo $fruits[0]; // Apple
?>
    

Associative arrays use named keys instead of numeric indexes.

<?php
$user = [
  "name" => "Zohil",
  "age" => 20
];

echo $user["name"]; // Zohil
?>
    

Forms allow users to send data to the server.

<form method="post" action="process.php">
  Name: <input type="text" name="name">
  <input type="submit">
</form>

<?php
// process.php
$name = $_POST['name'];
echo "Hello, $name!";
?>
    

Always validate user input to avoid errors or attacks.

<?php
$name = $_POST['name'];

if(empty($name)) {
  echo "Name is required";
} else {
  echo "Hello, $name!";
}
?>
    

The foreach loop is used to iterate over arrays easily.

<?php
$fruits = ["Apple", "Banana", "Orange"];

foreach($fruits as $fruit) {
  echo $fruit . "<br>";
}
?>
    

Use foreach to get both keys and values from associative arrays.

<?php
$user = ["name" => "Zohil", "age" => 20];

foreach($user as $key => $value) {
  echo "$key : $value <br>";
}
?>
    

Superglobals store data from forms, URLs, sessions, and more.

<?php
// URL: test.php?name=Zohil
echo $_GET['name']; // Zohil

// POST example comes from a form
echo $_POST['age'];
?>
    

PHP provides many functions to manipulate strings.

<?php
$name = "Zohil Rahimzai";

echo strlen($name); // Length
echo strtoupper($name); // Uppercase
echo strtolower($name); // Lowercase
echo str_replace("Zohil","Ali",$name); // Replace
?>
    

PHP has built-in functions to handle arrays efficiently.

<?php
$fruits = ["Apple","Banana","Orange"];
array_push($fruits,"Mango"); // Add
array_pop($fruits); // Remove last
echo count($fruits); // Count elements
print_r($fruits); // Print array
?>
    

Use include or require to reuse code from other files.

<?php
// header.php
echo "<h1>Welcome</h1>";

// index.php
include 'header.php';
echo "Home Page";
?>
    

Sessions store user data across multiple pages.

<?php
session_start();
$_SESSION['user'] = "Zohil";

echo $_SESSION['user']; // Zohil
?>
    

Cookies store small data on the user’s browser.

<?php
setcookie("user", "Zohil", time()+3600); // 1 hour
echo $_COOKIE['user'];
?>
    

Object-Oriented Programming (OOP) allows organizing code with classes and objects.

<?php
class User {
  public $name;

  function __construct($name) {
    $this->name = $name;
  }

  function greet() {
    return "Hello, ".$this->name;
  }
}

$user = new User("Zohil");
echo $user->greet();
?>
    

Classes have properties (data) and methods (functions).

<?php
class Car {
  public $color;
  
  function setColor($color) {
    $this->color = $color;
  }

  function getColor() {
    return $this->color;
  }
}

$car = new Car();
$car->setColor("Red");
echo $car->getColor(); // Red
?>
    

Visibility controls access to class properties and methods.

<?php
class User {
  public $name;
  private $password;
  
  function setPassword($pass) {
    $this->password = $pass;
  }

  function getPassword() {
    return $this->password;
  }
}

$user = new User();
$user->name = "Zohil";
$user->setPassword("1234");
echo $user->getPassword();
?>
    

Inheritance allows a class to use properties and methods of another class.

<?php
class Person {
  public $name;
  
  function greet() {
    return "Hello, ".$this->name;
  }
}

class Student extends Person {
  public $grade;
}

$student = new Student();
$student->name = "Zohil";
echo $student->greet();
?>
    

Static members belong to the class itself, not objects.

<?php
class Math {
  public static $pi = 3.14;

  public static function square($n) {
    return $n * $n;
  }
}

echo Math::$pi;
echo Math::square(5);
?>
    

PHP can read and write files on the server.

<?php
// Write to file
file_put_contents("test.txt", "Hello, PHP!");

// Read from file
echo file_get_contents("test.txt");
?>
    

Use try-catch blocks to handle errors gracefully.

<?php
try {
  if(!file_exists("data.txt")) {
    throw new Exception("File not found!");
  }
} catch (Exception $e) {
  echo "Error: ".$e->getMessage();
}
?>
    

Use mysqli or PDO to connect PHP with MySQL databases.

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

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

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

Insert data into MySQL using PHP.

<?php
$sql = "INSERT INTO users (name, age) VALUES ('Zohil', 20)";
if ($conn->query($sql) === TRUE) {
  echo "New record created";
} else {
  echo "Error: ".$conn->error;
}
?>
    

Fetch data from MySQL using PHP.

<?php
$sql = "SELECT * FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
  while($row = $result->fetch_assoc()) {
    echo "Name: ".$row["name"]." - Age: ".$row["age"]."<br>";
  }
} else {
  echo "0 results";
}
?>
    

Update existing data in MySQL using PHP.

<?php
$sql = "UPDATE users SET age=21 WHERE name='Zohil'";
if ($conn->query($sql) === TRUE) {
  echo "Record updated";
} else {
  echo "Error: ".$conn->error;
}
?>
    

Delete data securely using prepared statements to prevent SQL injection.

<?php
$stmt = $conn->prepare("DELETE FROM users WHERE name=?");
$stmt->bind_param("s", $name);

$name = "Zohil";
$stmt->execute();

echo "Record deleted";
$stmt->close();
?>
    

PHP can encode and decode JSON for APIs and data exchange.

<?php
$data = ["name"=>"Zohil", "age"=>20];

// Convert array to JSON
$json = json_encode($data);
echo $json;

// Convert JSON back to array
$arr = json_decode($json, true);
print_r($arr);
?>
    

PHP can handle file uploads from HTML forms.

<form method="post" enctype="multipart/form-data">
  Select file: <input type="file" name="file">
  <input type="submit">
</form>

<?php
if(isset($_FILES['file'])) {
  move_uploaded_file($_FILES['file']['tmp_name'], "uploads/".$_FILES['file']['name']);
  echo "File uploaded!";
}
?>
    

PHP can request data from APIs using file_get_contents or cURL.

<?php
$url = "https://api.example.com/data";
$response = file_get_contents($url);
$data = json_decode($response, true);
print_r($data);
?>
    

PHP can send emails using the mail() function.

<?php
$to = "user@example.com";
$subject = "Test Email";
$message = "Hello from PHP!";
$headers = "From: admin@example.com";

if(mail($to, $subject, $message, $headers)) {
  echo "Email sent!";
} else {
  echo "Email failed!";
}
?>
    

Build a complete project to master everything you learned:

Project: User Management System

Features:
- Register/Login (with session & password hashing)
- CRUD Users (PHP + MySQL)
- File Uploads
- API integration (JSON)
- Email notifications
- Validation & Security

Tech Stack:
PHP + MySQL + HTML/CSS + JS