notes-shivam

unit 1

4 min read

Introduction to PHP

1. What is PHP

  1. PHP (Hypertext Preprocessor) is a server-side scripting language used to build dynamic web applications.

  2. It is executed on the server and returns HTML output to the browser.

  3. Widely used with databases like MySQL for full-stack web development.

Key Features

  1. Open source

  2. Platform independent

  3. Embedded in HTML

  4. Supports databases (MySQL, PostgreSQL, etc.)

  5. Interpreted language (no compilation required)

2. Installing and Configuring PHP

  1. Download XAMPP

  2. Install and open XAMPP Control Panel

  3. Start:

    • Apache (Web Server)

    • MySQL (Database)

  4. Place PHP files inside:

C:\xampp\htdocs\
  1. Run in browser:
http://localhost/filename.php

2.2 Verify Installation

Create file: test.php

<?php
phpinfo();
?>

Open in browser → displays PHP configuration details.

3. Building Blocks of PHP

3.1 PHP Tags

PHP code is written inside special tags.

Types of PHP Tags

  1. Standard Tag (Recommended)
<?php
echo "Hello World";
?>
  1. Short Tag (Not always enabled)
<?
echo "Hello";
?>
  1. Echo Tag
<?= "Hello World"; ?>

3.2 Variables in PHP

Definition

Variables are used to store data.

Rules

  1. Starts with $

  2. Must begin with letter or underscore

  3. Cannot start with number

  4. Case-sensitive

Example

<?php
$name = "Shivam";
$age = 21;
 
echo $name;
echo $age;
?>

3.3 Data Types in PHP

Types

  1. String
$name = "PHP";
  1. Integer
$age = 21;
  1. Float (Double)
$price = 99.99;
  1. Boolean
$isActive = true;
  1. Array
$colors = array("red", "blue", "green");
  1. NULL
$x = null;

3.4 Constants

Definition

Constants are values that cannot be changed once defined.

Syntax

define("PI", 3.14);
echo PI;

3.5 Operators in PHP

1. Arithmetic Operators

$a = 10;
$b = 5;
 
echo $a + $b; // 15
echo $a - $b; // 5
echo $a * $b; // 50
echo $a / $b; // 2

2. Assignment Operator

$x = 10;
$x += 5; // x = 15

3. Comparison Operators

$a == $b   // equal
$a != $b   // not equal
$a > $b
$a < $b

4. Logical Operators

($a > 5 && $b < 10)
($a > 5 || $b < 10)
!($a > 5)

3.6 Expressions

Definition

An expression is a combination of variables, values, and operators that produces a result.

$result = ($a + $b) * 2;

4. Control Structures

4.1 Conditional Statements

1. if Statement

<?php
$age = 18;
 
if ($age >= 18) {
    echo "Eligible to vote";
}
?>

2. if-else Statement

if ($age >= 18) {
    echo "Adult";
} else {
    echo "Minor";
}

3. if-elseif-else

$marks = 75;
 
if ($marks >= 90) {
    echo "A Grade";
} elseif ($marks >= 60) {
    echo "B Grade";
} else {
    echo "Fail";
}

4.2 Switch Statement

Definition

Used when multiple conditions are based on same variable.

$day = 2;
 
switch ($day) {
    case 1:
        echo "Monday";
        break;
    case 2:
        echo "Tuesday";
        break;
    default:
        echo "Invalid";
}

4.3 Loops in PHP

1. for Loop

for ($i = 1; $i <= 5; $i++) {
    echo $i;
}

2. while Loop

$i = 1;
 
while ($i <= 5) {
    echo $i;
    $i++;
}

3. do-while Loop

$i = 1;
 
do {
    echo $i;
    $i++;
} while ($i <= 5);

4. foreach Loop (for arrays)

$colors = ["red", "blue", "green"];
 
foreach ($colors as $color) {
    echo $color;
}

5. Complete Working Program

Problem: Student Result System

Features Covered

  • Variables

  • Data types

  • Constants

  • Operators

  • Conditional statements

  • Switch

  • Loops

<?php
 
// Constant
define("PASS_MARKS", 40);
 
// Variables
$name = "Shivam";
$marks = [85, 72, 60, 30, 90];
 
// Calculate total
$total = 0;
 
foreach ($marks as $m) {
    $total += $m;
}
 
// Calculate average
$average = $total / count($marks);
 
// Output
echo "Name: $name <br>";
echo "Total Marks: $total <br>";
echo "Average: $average <br>";
 
// Result using if-else
if ($average >= 75) {
    $grade = "A";
} elseif ($average >= 60) {
    $grade = "B";
} elseif ($average >= PASS_MARKS) {
    $grade = "C";
} else {
    $grade = "Fail";
}
 
echo "Grade: $grade <br>";
 
// Switch example
switch ($grade) {
    case "A":
        echo "Excellent Performance";
        break;
    case "B":
        echo "Good Performance";
        break;
    case "C":
        echo "Average Performance";
        break;
    default:
        echo "Needs Improvement";
}
 
// Loop example
echo "<br>Marks:<br>";
for ($i = 0; $i < count($marks); $i++) {
    echo "Subject " . ($i + 1) . ": " . $marks[$i] . "<br>";
}
 
?>

6. Summary

  1. PHP is a server-side scripting language for web development

  2. Installed easily using XAMPP

  3. Core building blocks:

    • Tags

    • Variables

    • Data types

    • Constants

    • Operators

    • Expressions

  4. Control structures:

    • if, else, elseif

    • switch

    • loops (for, while, do-while, foreach)

  5. Used to build dynamic, database-driven web applications

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