Unit 02

File operations in PHP allow developers to create, open, read, write, close, copy, rename, and manipulate files on the server. PHP provides several built-in functions for performing these operations.

Common File Operations

$data = fread($file, 100);

$file = fopen("data.txt", "w");
fwrite($file, "Hello PHP");

file_put_contents("data.txt", "Hello PHP");

fclose($file);

<?php
$file = fopen("sample.txt", "w");
fwrite($file, "Welcome to PHP");
fclose($file);
?>

Cookies and sessions are used in PHP to store user-related information and maintain data across different web pages.

1. Cookies

A cookie is a small piece of information stored in the client's browser memory or hard disk. A cookie contains a name and value and can store information such as username, last visit time, and similar details.

Cookies allow information to be passed between different web pages.

<?php
setcookie("UserName", "IQRA", time() + 3600);
?>

Here, the cookie stores "IQRA" under the name UserName.

Accessing a cookie: echo $_COOKIE["UserName"];

To delete a cookie, its expiration time is set to a time in the past.

setcookie("UserName", "", time() - 3600);

2. Session

A session is a temporary storage area on the server used to store information about a user while they are visiting a website. Each user receives a unique Session ID, which allows the server to identify the user.

A session is started using session_start(), and session variables are created using the $_SESSION superglobal.

<?php
session_start();
$_SESSION["UserName"] = "IQRA";
?>

Accessing a session:

<?php
session_start();
echo $_SESSION["UserName"];
?>

A session can be destroyed using session_destroy();

Difference Between Cookie and Session

The mail() function is a built-in PHP function used to send emails directly from a PHP script. It sends email through the web server's configured mail service.

It is commonly used for contact forms, registration confirmation, password reset, OTP verification, notifications, and feedback forms.

Syntax

mail(to, subject, message, headers, parameters);

Parameters

Example

<?php
$to = "student@example.com";
$subject = "Welcome";
$message = "Welcome to our website!";
$headers = "From: admin@example.com";

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

The function returns TRUE if the email is accepted by the mail server and FALSE if it cannot be sent.

Email Headers

Headers provide additional information about the email. Common headers include From, Reply-To, CC, BCC, and Content-Type. Headers are passed as the fourth parameter of mail().

Exception handling is a mechanism used to handle unexpected events or errors that occur during program execution. These unexpected events are called exceptions and can disrupt the normal flow of a program.

PHP mainly uses try, throw, catch, and finally for exception handling.

1. try Block

The try block contains the code that may cause an exception.

try {
    $result = 10 / 2;
    echo $result;
}

2. throw Keyword

The throw keyword is used to manually generate an exception. PHP then looks for a catch block to handle it.

if ($age < 18) {
    throw new Exception("Age must be 18 or above");
}

3. catch Block

The catch block is executed when an exception occurs inside the try block. It is used to handle the exception.

catch (Exception $e) {
    echo "Exception occurred";
}

4. finally Block

The finally block always executes, whether an exception occurs or not. It is useful for cleanup operations such as closing a database connection.

finally {
    echo "Program Finished";
}

Complete Example

<?php
try {
    $age = 15;

    if ($age < 18) {
        throw new Exception("Age must be 18 or above");
    }

    echo "Valid Age";
}
catch (Exception $e) {
    echo "Exception occurred";
}
finally {
    echo "Program Finished";
}
?>