Jquery in web development, including Jquery in HTML

 jQuery is a lightweight, "write less, do more", JavaScript library.
 The purpose of jQuery is to make it much easier to use JavaScript on your website.
 jQuery takes a lot of common tasks that require many lines of JavaScript code to
accomplish, and wraps them into methods that you can call with a single line of code.
 jQuery also simplifies a lot of the complicated things from JavaScript, like AJAX calls
and DOM manipulation.
 The jQuery library contains the following features:
 HTML/DOM manipulation
 CSS manipulation
 HTML event methods
 Effects and animations
 AJAX
jQuery

jQuery Applications
There are lots of other JavaScript libraries out there, but jQuery is
probably the most popular, and also the most extendable.
Many of the biggest companies on the Web use jQuery, such as:
• Google
• Microsoft
• IBM
• Netflix

Adding jQuery to Your Web Pages
There are several ways to start using jQuery on your web site. You can:
 Download the jQuery library from jQuery.com
 Include jQuery from a CDN (Content Delivery Network)
Versions of jQuery
There are two versions of jQuery available for downloading:
Production version - this is for your live website because it has been minified and
compressed
Development version - this is for testing and development (uncompressed and readable
code

There are two ways of including jquery, either from google or microsoft.
Google CDN (Content Delivery Network)
<head> <script
src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></
script>
</head>
Microsoft CDN (Content Delivery Network)
<head>
<script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.3.1.min.js">
</script>
</head>
Adding jQuery to your website

The main methods for manipulating HTML content in jQuery are:
 html(): Sets or returns the content of selected elements
 $("selector").html() returns the HTML content of the first
matched element
 $("selector").html("new content") sets the HTML content of the
matched elements
 $("selector").html(function(index, currentcontent)) sets the
content using a function
 text(): Sets or returns the text content of selected elements
Manipulating HTML Content

EXAMPLE
// Set the content of an element
$("h2").html("Hello <b>World!</b>");
// Return the content of the first matched element
alert($("h2").html());
// Set content using a function
$("h2").html(function(n))
{
return "jQuery | html() Method" + " has index: " + n;
});

ADDING AND REMOVING CLASSES
 addClass(): Adds one or more class names to selected elements
 removeClass(): Removes one or more classes from selected elements
 toggleClass(): Toggles between adding/removing one or more classes from selected elements
// Add a class
$("a").addClass("bold");
// Remove a class
$("a").removeClass("bold");

Inserting and Replacing Content
jQuery provides several methods for inserting and replacing
HTML content:
append(): Inserts content at the end of selected elements
prepend(): Inserts content at the beginning of selected
elements
after(): Inserts content after selected elements
before(): Inserts content before selected elements
replaceWith(): Replaces selected elements with new content

// Append content
$("div").append("<p>Appended text</p>");
// Prepend content
$("div").prepend("<p>Prepended text</p>");
// Insert after
$("div").after("<p>Inserted after</p>");
// Replace with
$("div").replaceWith("<p>Replaced div</p>");
Example

PHP
PHP, which stands for "PHP: Hypertext Preprocessor," is a widely-used
open-source server-side scripting language primarily designed for web
development.
Server-Side Execution: PHP scripts are executed on the server, generating
HTML that is sent to the client's browser. This allows for dynamic content
generation based on user input or other variables.
Integration with HTML: PHP can be easily embedded within HTML code,
allowing developers to mix PHP and HTML seamlessly. This makes it easier
to create dynamic web pages.
Database Support: PHP has built-in support for various databases such as
MySQL, PostgreSQL, and SQLite, enabling developers to create data-driven
applications.
Cross-Platform Compatibility: PHP runs on various operating systems,
including Windows, Linux, and macOS, making it versatile for different
server environments.
Open Source: Being open-source means PHP is free to use, and it has a
large community of developers contributing to its continuous improvement
and extensive documentation.

Dynamic Web Pages: PHP is primarily used to create dynamic web
pages that can respond to user inputs and display different content
based on various conditions.
Form Handling: PHP can collect and process form data, making it
essential for applications that require user interaction.
Session Management: PHP can manage user sessions, allowing for
personalized experiences on websites.
File Handling: PHP can create, read, write, and delete files on the
server, facilitating various functionalities like file uploads and
downloads.
Uses of PHP

Basic Syntax
A typical PHP file has a .php extension and can contain HTML, CSS, JavaScript,
and PHP code. The basic syntax for embedding PHP in an HTML document is
<html>
<head>
<title>PHP Example</title>
</head>
<body>
<?php echo "Hello, World! This is PHP code.";?>
</body>
</html>

VARIABLES, CONSTANTS, DATA TYPES, AND ARRAYS IN PHP
 Variables
A variable in PHP is a container for storing data. It is defined by a
name that starts with a dollar sign ($), followed by the variable name.
PHP automatically assigns a data type to a variable based on the
value assigned to it.
 Rules for Naming Variables
Must start with a dollar sign ($).
Followed by a letter or an underscore, and can contain letters,
numbers, and underscores.
Variable names are case-sensitive (e.g., $myVar and $myvar are
different).

EXAMPL
E
$age = 25; // Integer
$name = "John"; // String
$height = 5.9; // Float
$isStudent = true; // Boolean

CONSTANTS
• Constants are similar to variables but are immutable; once
defined, their value cannot change during the execution of the
script.
• Constants are defined using the define() function or the const
keyword, and they do not require a dollar sign.
define("PI", 3.14); // Using define()
const GRAVITY = 9.81; // Using const

DATA TYPES
PHP Supports several data types, which can be categorized into simple, compound, and
special data types:
1.Simple Data Types
 Integer: Whole numbers, e.g., 42, -7.
 Float: Decimal numbers, e.g., 3.14, -0.001.
 String: Sequence of characters, e.g., "Hello, World!".
 Boolean: Represents two states, true or false.
2.Compound Data Types
 Array: A collection of values, which can be of mixed types.
 Object: An instance of a class.
3.Special Data Types
 NULL: Represents a variable with no value.
 Resource: A special variable that holds a reference to an external
resource, like a database connection.

EXAMPLE OF DATA
TYPES
$integerVar = 10; // Integer
$floatVar = 10.5; // Float
$stringVar = "Hello"; // String
$boolVar = true; // Boolean
$arrayVar = array(1, 2, 3); // Array
$nullVar = null; // NULL

ARRAYS
Arrays in PHP can store multiple values in a single variable. They can be indexed
(numerical) or associative (key-value pairs).
$colors = array("Red", "Green", "Blue");
echo $colors[0]; // Outputs: Red
$person = array("name" => "John", "age" => 30);
echo $person["name"]; // Outputs: John
Associative Array
Indexed Array

SETTING UP CONDITIONS IN PHP
SCRIPTS
Conditional statements are essential for controlling the flow of execution in PHP scripts. They
allow you to execute different blocks of code based on specific conditions. PHP provides several
conditional constructs to handle various scenarios:
if Statement
The if statement is the most basic conditional construct. It executes a
block of code if a specified condition is true.
$age = 18;
if ($age >= 18) {
echo "You are an adult.";
}

IF...ELSE STATEMENT
The if...else statement executes a block of code if a condition is true, and
another block if the condition is false.
$temperature = 25;
if ($temperature > 30)
{
echo "It's hot outside.";
}
else
{
echo "The weather is pleasant.";
}

IF...ELSEIF...ELSE STATEMENT
$grade = 85;
if ($grade >= 90)
{
echo "You got an A.";
} elseif ($grade >= 80)
{
echo "You got a B.";
} else
{
echo "You need to improve.";
}
The if...elseif...else statement executes different blocks of code based on
multiple conditions.

NESTED IF STATEMENTS
$age = 25;
$gender = "female";
if ($age >= 18) {
if ($gender == "female") {
echo "You are an adult female.";
} else {
echo "You are an adult male.";
}
}
nest if statements inside other if statements to create more complex
conditional logic.

SWITCH STATEMENT
The switch statement is an alternative to multiple if...elseif statements. It
executes different blocks of code based on different cases.
$day = 3;
switch ($day) {
case 1:
echo "Monday";
break;
case 2:
echo "Tuesday";
break;
case 3:
echo "Wednesday";
break;
default:
echo "Invalid day";
}

REPEATING ACTIONS WITH LOOP IN PHP
 Loops in PHP allow you to repeatedly execute a block of code until a
certain condition is met.
 This is useful when you need to perform an action multiple times or
iterate over a collection of data.
 PHP provides several types of loops
 for Loop
 while Loop
 do...while Loop
 foreach Loop

for Loop
The for loop is used when you know in advance how many times the loop
should execute. It consists of three parts separated by semicolons:
initialization, condition, and increment/decrement.
for ($i = 1; $i <= 5; $i++)
{
echo "Iteration $i<br>";
}
Output
Iteration 1
Iteration 2
Iteration 3
Iteration 4
Iteration 5

while Loop
The while loop continues to execute a block of code as long as a
specified condition is true.
$count = 1;
while ($count <= 3) {
echo "Count: $count<br>";
$count++;
}
Output
Count: 1
Count: 2
Count: 3

do...while Loop
The do...while loop is similar to the while loop, but it guarantees that the
code block is executed at least once before the condition is tested.
$i = 1;
do {
echo "Value of i: $i<br>";
$i++;
} while ($i <= 5);
Output
Value of i: 1
Value of i: 2
Value of i: 3
Value of i: 4
Value of i: 5

foreach Loop
The foreach loop is specifically designed for iterating over arrays and objects. It
automatically assigns each value of the array to a variable.
$fruits = array("apple", "banana", "cherry");
foreach ($fruits as $fruit) {
echo "I like $fruit<br>";
}
Output
I like apple
I like banana
I like cherry

USING FUNCTIONS IN PHP
Functions in PHP are blocks of code designed to perform specific
tasks.
They enhance code reusability, maintainability, and
organization.
PHP supports two main types of functions: built-in functions
and user-defined functions.

 PHP comes with a vast library of built-in functions, which are
pre-defined and ready to use. These functions cover a wide range
of tasks, including string manipulation, mathematical
calculations, and file handling.
Examples
 strlen(): Returns the length of a string.
 array_push(): Adds one or more elements to the end of an array.
 var_dump(): Displays structured information about one or more
variables.
Built-in Functions

USER-DEFINED FUNCTIONS
User-defined functions allow you to create your own functions tailored to
your specific needs.
function
functionName($parameter1,
$parameter2) {
// code to be executed
}
function sample($name) {
echo "Hello, $name!";
}
// Calling the function
sample("Abc");
Syntax Example

FUNCTION PARAMETERS
Functions can accept parameters, which are variables passed into the
function. You can define multiple parameters, separated by commas.
function add($a, $b)
{
return $a + $b;
}
$result = add(5, 10);
echo "The sum is: $result"; // Outputs: The sum is: 15

DEFAULT PARAMETER VALUES
You can set default values for parameters. If a value is not
provided during the function call, the default value will be used.
function greet($name = "Guest")
{
echo "Hello, $name!";
}
greet(); // Outputs: Hello, Guest!
greet("Bob"); // Outputs: Hello, Bob!

RETURNING VALUES
Functions can return values using the return statement. Once a return
statement is executed, the function stops executing.
function square($number)
{
return $number * $number;
}
echo "The square of 4 is: " . square(4); // Outputs: The square of 4 is: 16

CALL BY VALUE VS. CALL BY REFERENCE
By default, PHP passes arguments to functions by value, meaning a copy of the variable is
passed. If you want to pass a variable by reference (allowing the function to modify the
original variable), you can use the & symbol.
function increment(&$value)
{
$value++;
}
$num = 5;
increment($num);
echo $num; // Outputs: 6

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