Server Side Programming in PHP

1. What is PHP?

PHP (PHP: Hypertext Preprocessor) is an open-source, server-side scripting language embedded in HTML, executed on the web server; only the resulting HTML is sent to the browser. Runs everywhere via the AMP stack (Apache + MySQL + PHP). Files use the .php extension.

Feature	Detail
Server-side	Code runs on the server; browser sees only output
Embedded in HTML	`<?php ... ?>` blocks inside `.php` pages
Loosely typed	`$x = 5;$ x = "hi";` — types auto-converted
Cross-platform & free	Windows/Linux/Apache/IIS/Nginx
Database support	MySQL/MariaDB (`mysqli`, PDO), PostgreSQL, Oracle
Large ecosystem	Sessions, cookies, file upload, mail, GD images, CMSs (WordPress, Drupal)

2. Basic Syntax

<?php
  echo "Hello, World!";              // output
  $name = "Asha";  $marks = 92;      // variables start with $
  echo "<p>$name scored $marks</p>"; // interpolation in double quotes
  /* multi-line comment */
  # single-line comment too
?>

Data types: int, float, string, bool, array, object, NULL. String functions: strlen, strtoupper, substr, trim, explode, implode, strcmp, str_replace. Math: abs, round, rand, sqrt, max, min.

if ($marks >= 90)      echo "Distinction";
elseif ($marks >= 60)  echo "First class";
else                   echo "Pass";

for ($i = 1; $i <= 5; $i++) echo $i;
foreach ($colors as $c) echo $c;

function area($w, $h) { return $w * $h; }   // user-defined function

$marks = array(88, 92, 75);                 // indexed array
$student = array("roll" => 12, "name" => "Asha");   // associative array
echo $student["name"];  sort($marks);  count($marks);

<!-- welcome.php -->
<?php
  $nm = $_POST["nm"];  $em = $_POST["em"];
  echo "Welcome, $nm ($em)";
?>

$_GET` → values in the URL query string (bookmarkable, limited length); `$ _POST → values in the HTTP body (no length limit, not shown in URL, preferred for sensitive data); $_REQUEST → either.

// cookie: stored on the client
setcookie("user", "Asha", time() + 3600);       // 1 hour
echo $_COOKIE["user"];

// session: stored on the server; id kept in a cookie
session_start();
$_SESSION["roll"] = 12;
echo $_SESSION["roll"];
session_destroy();                              // logout

7. Other Practical Features

File upload: <form enctype="multipart/form-data"> → move_uploaded_file($_FILES['pic']['tmp_name'], "uploads/pic.jpg").
File read/write: fopen, fread, fwrite, fclose, file_get_contents.
E-mail: mail( $to,$ subject, $msg,$ headers).
Include files: include 'header.php'; require 'db.php';.
Header/redirect: header("Location: login.php");.

8. PHP vs Client-side JavaScript vs JSP

Aspect	PHP	JavaScript	JSP
Runs on	Server	Browser	Server (Java)
Compiled?	Interpreted (op-cached)	Interpreted	Compiled to servlet bytecode
DB access	Yes	No	Yes (JDBC)
Best for	Rapid web apps	UI/validation	Enterprise Java apps

9. Exam Points

Explain the features of PHP with syntax examples — 7-10 marks.
Write a PHP program to handle a form (login / registration) with $_POST — 10 marks (very frequent program).
Write PHP+MySQL code to insert/display records — 10 marks.
Cookies vs sessions in PHP with code — 5 marks.
GET vs POST handling in PHP — 5 marks.

Server Side Programming in PHP