Basics
- Example 1: Printing “Hello, World!” using
echo
:
echo "Hello, World!";
- Example 2: Assigning and displaying variables:
$name = "John Doe"; echo "My name is " . $name;
- Example 3: Writing comments in PHP code:
// This is a single-line comment /* This is a multi-line comment */
- Example 4: Using the
print
statement:
print "Welcome to PHP";
- Example 5: Getting the current date and time:
$currentDate = date("Y-m-d H:i:s"); echo "Current date and time: " . $currentDate;
Variables and Constants
- Example 1: Declaring and using variables:
$name = "John Doe"; $age = 25; $salary = 5000.50; echo "Name: " . $name . ", Age: " . $age . ", Salary: $" . $salary;
- Example 2: Defining and using constants:
define("PI", 3.14); echo "The value of PI is: " . PI;
- Example 3: Variable scope (local and global):
$globalVariable = "I am a global variable"; function myFunction() { $localVariable = "I am a local variable"; echo $localVariable; echo $GLOBALS['globalVariable']; } myFunction();
- Example 4: Variable interpolation:
$name = "John Doe"; echo "My name is $name";
- Example 5: Constants case sensitivity:
define("MY_CONSTANT", "Hello"); echo MY_CONSTANT; echo my_constant;
Operators
- Example 1: Arithmetic operators:
$num1 = 10; $num2 = 5; echo $num1 + $num2; // Addition echo $num1 - $num2; // Subtraction echo $num1 * $num2; // Multiplication echo $num1 / $num2; // Division echo $num1 % $num2; // Modulo
- Example 2: Assignment operators:
$num = 10; $num += 5; // Equivalent to $num = $num + 5; echo $num; $str = "Hello"; $str .= " World"; // Equivalent to $str = $str . " World"; echo $str;
- Example 3: Comparison operators:
$num1 = 10; $num2 = 5; var_dump($num1 == $num2); // Equal to var_dump($num1 != $num2); // Not equal to var_dump($num1 > $num2); // Greater than var_dump($num1 < $num2); // Less than var_dump($num1 >= $num2); // Greater than or equal to var_dump($num1 <= $num 2); // Less than or equal to
- Example 4: Logical operators:
$num1 = 10; $num2 = 5; $num3 = 7; var_dump($num1 > $num2 && $num1 < $num3); // Logical AND var_dump($num1 > $num2 || $num1 > $num3); // Logical OR var_dump(!($num1 > $num2)); // Logical NOT
- Example 5: String operators:
$str1 = "Hello"; $str2 = "World"; echo $str1 . $str2; // Concatenation echo $str1 .= $str2; // Concatenation and assignment
Conditionals
- Example 1: If-else statement:
$num = 10; if ($num > 0) { echo "The number is positive"; } else { echo "The number is not positive"; }
- Example 2: Switch case statement:
$day = "Monday"; switch ($day) { case "Monday": echo "Today is Monday"; break; case "Tuesday": echo "Today is Tuesday"; break; default: echo "Today is not Monday or Tuesday"; }
- Example 3: Ternary operator:
$num = 10; $result = ($num % 2 == 0) ? "Even" : "Odd"; echo $result;
- Example 4: Multiple conditions in if statement:
$num = 10; if ($num > 0 && $num < 20) { echo "The number is between 0 and 20"; }
- Example 5: Nested if-else statements:
$num = 10; if ($num > 0) { if ($num < 20) { echo "The number is between 0 and 20"; } }
Loop Constructs
- Example 1: For loop:
for ($i = 1; $i <= 5; $i++) { echo $i . " "; }
- Example 2: While loop:
$i = 1; while ($i <= 5) { echo $i . " "; $i++; }
- Example 3: Do-while loop:
$i = 1; do { echo $i . " "; $i++; } while ($i <= 5);
- Example 4: Foreach loop with an array:
$numbers = [1, 2, 3, 4, 5]; foreach ($numbers as $number) { echo $number . " "; }
- Example 5: Loop control statements (break and continue):
for ($i = 1; $i <= 10; $i++) { if ($i == 5) { break; // Exit the loop } if ($i % 2 == 0) { continue; // Skip the rest of the iteration } echo $i . " "; }
Arrays
- Example 1: Creating an indexed array:
$fruits = ["Apple", "Banana", "Orange"];
- Example 2: Accessing array elements:
$fruits = ["Apple", "Banana", "Orange"]; echo $fruits[0]; // Output: Apple
- Example 3: Modifying array elements:
$fruits = ["Apple", "Banana", "Orange"]; $fruits[1] = "Mango";
- Example 4: Counting array elements:
$fruits = ["Apple", "Banana", "Orange"]; $count = count($fruits); echo $count; // Output: 3
- Example 5: Searching for a value in an array:
$fruits = ["Apple", "Banana", "Orange"]; $index = array_search("Banana", $fruits); echo $index; // Output: 1
Multi-Dimensional Arrays
- Example 1: Creating a 2D array:
$matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ];
- Example 2: Accessing elements in a 2D array:
$matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ]; echo $matrix[1][2]; // Output: 6
- Example 3: Modifying elements in a 2D array:
$matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ]; $matrix[2][1] = 10;
- Example 4: Counting elements in a 2D array:
$matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ]; $count = count($matrix, COUNT_RECURSIVE); echo $count; // Output: 9
- Example 5: Searching for a value in a 2D array:
$matrix = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ]; $index = array_search(6, array_merge(...$matrix)); echo $index; // Output: 5
Associative Arrays
- Example 1: Creating an associative array:
$student = [ "name" => "John Doe", "age" => 20, "city" => "New York" ];
- Example 2: Accessing values in an associative array:
$student = [ "name" => "John Doe", "age" => 20, "city" => "New York" ]; echo $student["name"]; // Output: John Doe
- Example 3: Modifying values in an associative array:
$student = [ "name" => "John Doe", "age" => 20, "city" => "New York" ]; $student["age"] = 21;
- Example 4: Counting elements in an associative array:
$student = [ "name" => "John Doe", "age" => 20, "city" => "New York" ]; $count = count($student); echo $count; // Output: 3
- Example 5: Checking if a key exists in an associative array:
$student = [ "name" => "John Doe", "age" => 20, "city" => "New York" ]; $exists = array_key_exists("age", $student); echo $exists; // Output: 1 (true)
Array of Associative Arrays
- Example 1: Creating an array of associative arrays:
$students = [ [ "name" => "John Doe", "age" => 20, "city" => "New York" ], [ "name" => "Jane Smith", "age" => 22, "city" => "Los Angeles" ], [ "name" => "Mike Johnson", "age" => 19, "city" => "Chicago" ] ];
- Example 2: Accessing values in an array of associative arrays:
$students = [ [ "name" => "John Doe", "age" => 20, "city" => "New York" ], [ "name" => "Jane Smith", "age" => 22, "city" => "Los Angeles" ], [ "name" => "Mike Johnson", "age" => 19, "city" => "Chicago" ] ]; echo $students[1]["name"]; // Output: Jane Smith
- Example 3: Modifying values in an array of associative arrays:
$students = [ [ "name" => "John Doe", "age" => 20, "city" => "New York" ], [ "name" => "Jane Smith", "age" => 22, "city" => "Los Angeles" ], [ "name" => "Mike Johnson", "age" => 19, "city" => "Chicago" ] ]; $students[2]["age"] = 20;
- Example 4: Counting elements in an array of associative arrays:
$students = [ [ "name" => "John Doe", "age" => 20, "city" => "New York" ], [ "name" => "Jane Smith", "age" => 22, "city" => "Los Angeles" ], [ "name" => "Mike Johnson", "age" => 19, "city" => "Chicago" ] ]; $count = count($students); echo $count; // Output: 3
- Example 5: Searching for a value in an array of associative arrays:
$students = [ [ "name" => "John Doe", "age" => 20, "city" => "New York" ], [ "name" => "Jane Smith", "age" => 22, "city" => "Los Angeles" ], [ "name" => "Mike Johnson", "age" => 19, "city" => "Chicago" ] ]; $index = array_search("Los Angeles", array_column($students, "city")); echo $index; // Output: 1
Functions
- Example 1: Creating a function:
function sayHello() { echo "Hello, World!"; } sayHello();
- Example 2: Function with parameters:
function greet($name) { echo "Hello, " . $name . "!"; } greet("John");
- Example 3: Returning a value from a function:
function add($num1, $num2) { return $num1 + $num2; } $result = add(3, 5); echo $result; // Output: 8
- Example 4: Function with default parameter value:
function greet($name = "Guest") { echo "Hello, " . $name . "!"; } greet(); // Output: Hello, Guest! greet("John"); // Output: Hello, John!
- Example 5: Recursive function:
function factorial($num) { if ($num <= 1) { return 1; } return $num * factorial($num - 1); } $result = factorial(5); echo $result; // Output: 120
Classes
- Example 1: Creating a class:
class Person { public $name; public $age; public function sayHello() { echo "Hello, my name is " . $this->name . " and I am " . $this->age . " years old."; } } $person = new Person(); $person->name = "John"; $person->age = 25; $person->sayHello();
- Example 2: Constructors and property accessors:
class Person { private $name; private $age; public function __construct($name, $age) { $this->name = $name; $this->age = $age; } public function getName() { return $this->name; } public function getAge() { return $this->age; } } $person = new Person("John", 25); echo $person->getName(); // Output: John echo $person->getAge(); // Output: 25
- Example 3: Inheritance:
class Animal { public function makeSound() { echo "The animal makes a sound."; } } class Dog extends Animal { public function makeSound() { echo "The dog barks."; } } $dog = new Dog(); $dog->makeSound(); // Output: The dog barks.
- Example
4: Static properties and methods:
class MathUtils { public static $pi = 3.14159; public static function square($num) { return $num * $num; } } echo MathUtils::$pi; // Output: 3.14159 echo MathUtils::square(5); // Output: 25
- Example 5: Abstract classes and interfaces:
abstract class Animal { abstract public function makeSound(); } interface CanFly { public function fly(); } class Bird extends Animal implements CanFly { public function makeSound() { echo "The bird chirps."; } public function fly() { echo "The bird is flying."; } } $bird = new Bird(); $bird->makeSound(); // Output: The bird chirps. $bird->fly(); // Output: The bird is flying.
File Handling
- Example 1: Reading from a file:
$file = fopen("data.txt", "r"); while (!feof($file)) { $line = fgets($file); echo $line; } fclose($file);
- Example 2: Writing to a file:
$file = fopen("data.txt", "w"); fwrite($file, "Hello, World!"); fclose($file);
- Example 3: Appending to a file:
$file = fopen("data.txt", "a"); fwrite($file, "New content"); fclose($file);
- Example 4: Checking if a file exists:
if (file_exists("data.txt")) { echo "File exists."; } else { echo "File does not exist."; }
- Example 5: Deleting a file:
unlink("data.txt");
Database Connection (MySQL)
- Connecting to the database:
$servername = "localhost"; $username = "your_username"; $password = "your_password"; $dbname = "your_database"; try { $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password); $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); echo "Connected successfully"; } catch (PDOException $e) { echo "Connection failed: " . $e->getMessage(); }
- Selecting all users from the “users” table:
try { $stmt = $conn->query("SELECT * FROM users"); $users = $stmt->fetchAll(PDO::FETCH_ASSOC); foreach ($users as $user) { echo "ID: " . $user['id'] . " - Name: " . $user['name'] . " - Age: " . $user['age'] . " - City: " . $user['city'] . " - Salary: " . $user['salary'] . "<br>"; } } catch (PDOException $e) { echo "Error: " . $e->getMessage(); }
- Deleting a user from the “users” table:
try { $id = 1; $stmt = $conn->prepare("DELETE FROM users WHERE id = :id"); $stmt->bindParam(':id', $id); $stmt->execute(); echo "User deleted successfully"; } catch (PDOException $e) { echo "Error: " . $e->getMessage(); }
- Adding a new user to the “users” table:
try { $name = "John Doe"; $age = 25; $city = "New York"; $salary = 5000; $stmt = $conn->prepare("INSERT INTO users (name, age, city, salary) VALUES (:name, :age, :city, :salary)"); $stmt->bindParam(':name', $name); $stmt->bindParam(':age', $age); $stmt->bindParam(':city', $city); $stmt->bindParam(':salary', $salary); $stmt->execute(); echo "New user added successfully"; } catch (PDOException $e) { echo "Error: " . $e->getMessage(); }
- Fetching a single user from the “users” table:
try { $id = 1; $stmt = $conn->prepare("SELECT * FROM users WHERE id = :id"); $stmt->bindParam(':id', $id); $stmt->execute(); $user = $stmt->fetch(PDO::FETCH_ASSOC); if ($user) { echo "ID: " . $user['id'] . " - Name: " . $user['name'] . " - Age: " . $user['age'] . " - City: " . $user['city'] . " - Salary: " . $user['salary']; } else { echo "User not found"; } } catch (PDOException $e) { echo "Error: " . $e->getMessage(); }
Remember to replace “your_username”, “your_password”, and “your_database” with your actual MySQL credentials and database name. Additionally, ensure that PDO extension is enabled in your PHP configuration.