PHP Code Examples | Developer Resource

PHP Basics

Fundamental concepts and syntax examples

Variables & Echo

              <?php
// Defining variables
$name = "John Doe";
$age = 30;
$isActive = true;
$salary = 75000.50;

// Outputting variables
echo "Name: " . $name . "<br>";
echo "Age: $age years old<br>";
echo "Active status: " . ($isActive ? "Active" : "Inactive") . "<br>";
echo "Salary: $" . number_format($salary, 2);
?>            

              Basic variable declaration and string output with concatenation and interpolation.
            

Control Structures

              <?php
$score = 85;

// If-else statement
if ($score >= 90) {
  echo "Grade: A";
} elseif ($score >= 80) {
  echo "Grade: B";
} elseif ($score >= 70) {
  echo "Grade: C";
} elseif ($score >= 60) {
  echo "Grade: D";
} else {
  echo "Grade: F";
}

// Switch statement
$day = date("l");
switch ($day) {
  case "Monday":
    echo "<br>Start of work week";
    break;
  case "Friday":
    echo "<br>End of work week";
    break;
  case "Saturday":
  case "Sunday":
    echo "<br>Weekend!";
    break;
  default:
    echo "<br>Midweek";
}
?>            

              Examples of if-else statements and switch case for flow control.
            

Functions

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

// Function with default parameter
function calculateTotal($prices, $taxRate = 0.08) {
  $subtotal = array_sum($prices);
  $tax = $subtotal * $taxRate;
  return $subtotal + $tax;
}

// Using arrow functions (PHP 7.4+)
$multiply = fn($a, $b) => $a * $b;

// Using the functions
echo greet("Maria") . "<br>";

$prices = [10.99, 24.50, 35.00];
echo "Total with tax: $" . calculateTotal($prices) . "<br>";
echo "5 × 4 = " . $multiply(5, 4);
?>            

              Creating and using functions, including default parameters and arrow functions.
            

Arrays & Loops

Working with data collections and iteration

Array Manipulation

<?php // Indexed array $fruits = ["apple", "banana", "orange", "mango"]; echo $fruits[1] . " "; // banana // Associative array $person = [ "name" => "Alice Smith", "age" => 28, "email" => "[email protected]", "hobbies" => ["reading", "hiking", "photography"] ]; echo $person["name"] . " is " . $person["age"] . " years old "; echo "Favorite hobby: " . $person["hobbies"][0] . " "; // Array functions $numbers = [5, 2, 8, 1, 9]; sort($numbers); echo "Sorted: " . implode(", ", $numbers) . " "; $sum = array_sum($numbers); echo "Sum: $sum "; $filteredNumbers = array_filter($numbers, fn($n) => $n > 5); echo "Numbers > 5: " . implode(", ", $filteredNumbers) . " "; $doubledNumbers = array_map(fn($n) => $n * 2, $numbers); echo "Doubled: " . implode(", ", $doubledNumbers); ?>

Creating and manipulating indexed and associative arrays with built-in functions.

Loops

              <?php
// For loop
echo "For loop:<br>";
for ($i = 1; $i <= 5; $i++) {
  echo "$i ";
}
echo "<br><br>";

// While loop
echo "While loop:<br>";
$counter = 1;
while ($counter <= 5) {
  echo "$counter ";
  $counter++;
}
echo "<br><br>";

// Do-while loop
echo "Do-while loop:<br>";
$j = 1;
do {
  echo "$j ";
  $j++;
} while ($j <= 5);
echo "<br><br>";

// Foreach loop with indexed array
echo "Foreach with indexed array:<br>";
$colors = ["red", "green", "blue", "yellow"];
foreach ($colors as $color) {
  echo "$color ";
}
echo "<br><br>";

// Foreach loop with associative array
echo "Foreach with associative array:<br>";
$capitals = [
  "USA" => "Washington D.C.",
  "UK" => "London",
  "France" => "Paris",
  "Japan" => "Tokyo"
];

foreach ($capitals as $country => $capital) {
  echo "The capital of $country is $capital<br>";
}
?>            

              Various loop structures for iterating through data.
            

Object-Oriented Programming

Classes, objects, inheritance, and more

Classes & Objects

<?php class User { // Properties private $username; private $email; protected $role = "member"; // Constructor public function __construct($username, $email) { $this->username = $username; $this->email = $email; } // Methods public function getUsername() { return $this->username; } public function getEmail() { return $this->email; } public function getRole() { return $this->role; } public function setEmail($email) { // Basic validation if (filter_var($email, FILTER_VALIDATE_EMAIL)) { $this->email = $email; return true; } return false; } // Static method public static function validateUsername($username) { return strlen($username) >= 4; } } // Creating an object $user = new User("johndoe", "[email protected]"); echo "Username: " . $user->getUsername() . " "; echo "Email: " . $user->getEmail() . " "; echo "Role: " . $user->getRole() . " "; // Using static method $validUsername = User::validateUsername("jane"); echo "Is 'jane' a valid username? " . ($validUsername ? "Yes" : "No") . " "; ?>

Implementing classes with properties, methods, and constructor in PHP.

Inheritance & Polymorphism

              <?php
// Base class
class Vehicle {
  protected $make;
  protected $model;
  protected $year;
  
  public function __construct($make, $model, $year) {
    $this->make = $make;
    $this->model = $model;
    $this->year = $year;
  }
  
  public function getInfo() {
    return "{$this->year} {$this->make} {$this->model}";
  }
  
  public function startEngine() {
    return "Engine started!";
  }
}

// Derived class
class Car extends Vehicle {
  private $numDoors;
  
  public function __construct($make, $model, $year, $numDoors) {
    parent::__construct($make, $model, $year);
    $this->numDoors = $numDoors;
  }
  
  public function getInfo() {
    return parent::getInfo() . " with {$this->numDoors} doors";
  }
  
  public function startEngine() {
    return "Car engine purrs quietly";
  }
}

// Another derived class
class Motorcycle extends Vehicle {
  private $type;
  
  public function __construct($make, $model, $year, $type) {
    parent::__construct($make, $model, $year);
    $this->type = $type;
  }
  
  public function getInfo() {
    return parent::getInfo() . " ({$this->type})";
  }
  
  public function startEngine() {
    return "Motorcycle engine roars loudly!";
  }
}

// Using the classes
$car = new Car("Toyota", "Camry", 2022, 4);
echo $car->getInfo() . "<br>";
echo $car->startEngine() . "<br><br>";

$motorcycle = new Motorcycle("Harley-Davidson", "Street Glide", 2021, "Cruiser");
echo $motorcycle->getInfo() . "<br>";
echo $motorcycle->startEngine() . "<br>";
?>            

              Implementing inheritance and method overriding for polymorphic behavior.
            

Interfaces & Traits

              <?php
// Interface
interface Payable {
  public function calculatePay();
  public function getPaymentInfo();
}

// Trait
trait Logger {
  private $logMessages = [];
  
  public function log($message) {
    $timestamp = date("Y-m-d H:i:s");
    $this->logMessages[] = "[$timestamp] $message";
  }
  
  public function getLogs() {
    return $this->logMessages;
  }
}

// Class implementing interface and using trait
class Employee implements Payable {
  use Logger;
  
  private $name;
  private $hourlyRate;
  private $hoursWorked;
  
  public function __construct($name, $hourlyRate, $hoursWorked) {
    $this->name = $name;
    $this->hourlyRate = $hourlyRate;
    $this->hoursWorked = $hoursWorked;
    $this->log("Created employee: $name");
  }
  
  public function calculatePay() {
    $pay = $this->hourlyRate * $this->hoursWorked;
    $this->log("Calculated pay for {$this->name}: \${$pay}");
    return $pay;
  }
  
  public function getPaymentInfo() {
    return "{$this->name} - \${$this->hourlyRate}/hour × {$this->hoursWorked} hours";
  }
}

// Using the class
$employee = new Employee("Sarah Johnson", 25.50, 40);
echo "Payment info: " . $employee->getPaymentInfo() . "<br>";
echo "Pay: $" . $employee->calculatePay() . "<br><br>";

echo "Logs:<br>";
foreach ($employee->getLogs() as $log) {
  echo $log . "<br>";
}
?>            

              Using interfaces for contracts and traits for code reuse.
            

Database Operations

Connecting and working with databases

PDO Database Connection

              <?php
// Database configuration
$host = "localhost";
$dbname = "example_db";
$username = "db_user";
$password = "db_password";

try {
  // Create PDO instance
  $pdo = new PDO(
    "mysql:host=$host;dbname=$dbname;charset=utf8",
    $username,
    $password,
    [
      PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
      PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
      PDO::ATTR_EMULATE_PREPARES => false
    ]
  );
  
  echo "Connected successfully to database<br>";
} catch (PDOException $e) {
  die("Connection failed: " . $e->getMessage());
}

// Example query
try {
  $stmt = $pdo->query("SELECT VERSION() as version");
  $row = $stmt->fetch();
  echo "Database version: " . $row["version"];
} catch (PDOException $e) {
  echo "Query failed: " . $e->getMessage();
}
?>            

              Establishing a secure database connection using PDO.
            

CRUD Operations

<?php /* Assuming we have a valid $pdo connection from previous example */ // CREATE - Insert new user function createUser($pdo, $username, $email, $password) { $hashedPassword = password_hash($password, PASSWORD_DEFAULT); $sql = "INSERT INTO users (username, email, password_hash, created_at) VALUES (:username, :email, :password_hash, NOW())"; try { $stmt = $pdo->prepare($sql); $stmt->execute([ ":username" => $username, ":email" => $email, ":password_hash" => $hashedPassword ]); return $pdo->lastInsertId(); } catch (PDOException $e) { // Log error and return false in production echo "Error creating user: " . $e->getMessage(); return false; } } // READ - Get user by ID function getUserById($pdo, $userId) { $sql = "SELECT id, username, email, created_at FROM users WHERE id = :id"; try { $stmt = $pdo->prepare($sql); $stmt->execute([":id" => $userId]); return $stmt->fetch(); } catch (PDOException $e) { echo "Error fetching user: " . $e->getMessage(); return false; } } // UPDATE - Update user email function updateUserEmail($pdo, $userId, $newEmail) { $sql = "UPDATE users SET email = :email, updated_at = NOW() WHERE id = :id"; try { $stmt = $pdo->prepare($sql); $stmt->execute([ ":email" => $newEmail, ":id" => $userId ]); return $stmt->rowCount() > 0; } catch (PDOException $e) { echo "Error updating user: " . $e->getMessage(); return false; } } // DELETE - Delete user function deleteUser($pdo, $userId) { $sql = "DELETE FROM users WHERE id = :id"; try { $stmt = $pdo->prepare($sql); $stmt->execute([":id" => $userId]); return $stmt->rowCount() > 0; } catch (PDOException $e) { echo "Error deleting user: " . $e->getMessage(); return false; } } // Example usage (commented out) /* // Create a new user $newUserId = createUser($pdo, "newuser", "[email protected]", "secure_password123"); echo "Created user with ID: $newUserId "; // Get the user $user = getUserById($pdo, $newUserId); echo "Username: " . $user["username"] . " "; // Update user email $updated = updateUserEmail($pdo, $newUserId, "[email protected]"); echo "User updated: " . ($updated ? "Yes" : "No") . " "; // Delete user $deleted = deleteUser($pdo, $newUserId); echo "User deleted: " . ($deleted ? "Yes" : "No") . " "; */ ?>

Create, Read, Update, Delete (CRUD) operations using prepared statements.

Contact Form Example

PHP form processing with validation

Form Processing Code

            <?php
// Initialize variables
$name = $email = $message = "";
$nameErr = $emailErr = $messageErr = "";
$formSubmitted = false;

// Form processing
if ($_SERVER["REQUEST_METHOD"] == "POST") {
  // Validate name
  if (empty($_POST["name"])) {
    $nameErr = "Name is required";
  } else {
    $name = test_input($_POST["name"]);
    // Check if name contains only letters and whitespace
    if (!preg_match("/^[a-zA-Z ]*$/", $name)) {
      $nameErr = "Only letters and white space allowed";
    }
  }
  
  // Validate email
  if (empty($_POST["email"])) {
    $emailErr = "Email is required";
  } else {
    $email = test_input($_POST["email"]);
    // Check if email address is valid
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
      $emailErr = "Invalid email format";
    }
  }
  
  // Validate message
  if (empty($_POST["message"])) {
    $messageErr = "Message is required";
  } else {
    $message = test_input($_POST["message"]);
  }
  
  // Check if form is valid
  if (empty($nameErr) && empty($emailErr) && empty($messageErr)) {
    $formSubmitted = true;
    // In real implementation, you would send email or save to database here
  }
}

// Function to sanitize input data
function test_input($data) {
  $data = trim($data);
  $data = stripslashes($data);
  $data = htmlspecialchars($data);
  return $data;
}
?>          