PHP Crash Course

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June 25, 2023

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Php

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)

  1. 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();
}
  1. 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();
}
  1. 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();
}
  1. 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();
}
  1. 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.

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