Introduction to PHP

Introduction to PHP

• PHP is a versatile scripting language, especially made for web development
• There is an overview of PHP, its history, core concepts, and relevance

Definition and Uses of PHP

• PHP (Hypertext Preprocessor) is a widely used server-side scripting language for web development
• It is used to create dynamic and interactive websites by embedding PHP code within HTML

Key Features of PHP

• Code executes on the server before output is sent to the browser
• Open-source and free, supported by a large community
• Works on Windows, macOS, Linux, and other platforms
• Easily connects with MySQL, PostgreSQL, and other databases
• PHP can be mixed with HTML to generate dynamic web pages
• Has built-in features to protect against common security threats

History and Evolution

• Rasmus Lerdorf created PHP in 1994 to manage his personal website
• PHP was originally known as "Personal Home Page Tools"
• PHP's ease of use and ability to interact with databases made it a popular choice for web development
• PHP was significantly evolved into comprehensive scripting language
• The first official version of PHP was released in 1995

Trends and Advancements

• PHP continues to evolve with new features
• The language supports web development, with frameworks like Laravel and Symfony providing tools for building complex applications

Tools Needed

• PHP Development Environment:
  • XAMPP or WAMP provides a local server environment with PHP, Apache, and MySQL
  • MAMP is for macOS users
  • LAMP is for Linux users
• Code Editors or IDEs:
  • Visual Studio Code is a lightweight, feature-rich editor
  • PHPStorm is a professional IDE tailored for PHP (paid)
  • Other options include Sublime Text and Atom
• Database Management Tools:
  • phpMyAdmin is a web-based tool for managing MySQL databases
  • MySQL Workbench is a standalone tool for designing and managing databases
• Web Browsers:
  • Edge, Chrome, Firefox, or any browser to test PHP web pages
• Extensions:
  • Live Server in VS Code and Live Server in Chrome

PHP File Basics

• PHP Files has the ability to contain text, HTML, JavaScript, and PHP code
• PHP code is executed on the server and the result returned to the browser as plain HTML
• PHP files have a .php file extension

Basic PHP Syntax

• A PHP script starts with <?php and ends with ?>
• File extension for PHP files is .php

Comments

• // for a one-line comment
• /* ... */ for a block comment

PHP Variables

• Variables store data values
• Variables can be declared using the dollar sign $, followed by a name
• Must begin with a letter or underscore
• Can only contain alpha-numeric characters and underscores (A-z, 0-9, and _)
• Should not contain white spaces
• Variables are case-sensitive ($y is different from $Y)

PHP Data Types

• PHP supports several data types including strings, integers, floats, booleans, and arrays
• PHP is a loosely typed language, so it is not necessary to declare what data type the variable is

Echo and Print Statements

• echo can output one or more strings
• print can only output one string and always returns 1
• echo is marginally faster compared to print, as echo does not return any value

PHP Expressions

• Generally, completely normal like other languages (+ - /*)
• More aggressive implicit type conversion

PHP Operators

• Increment/Decrement (++ --)
• String concatenation (.)
• Equality (== !=)
• Identity (=== !==)
• Ternary (? :)
• Side-effect Assignment (+= -= .= etc.)
• Ignore the rarely-used bitwise operators (<< >> ^ | &)

Increment / Decrement Example

• If $x = 12; and $y = 15 + $x++;, then the output will be $x is 13 and y is 27

Concatenation Example

• If $greet = 'Hello '. 'World!';, then the output will be Hello World!

Ternary Operator Uses and Features

• The ternary operator comes from C
• Allows conditional expressions and a one-line if-then-else

Side Effect Operators

• Side Effect Operators are pure contractions

Casting

• Division forces operands to be floating points
• expression values are converted silently and aggressively
• Concatenation operator converts operands to strings

Equality versus Identity

• The equality operator (==) in PHP is far more aggressive than in most other languages when converting data during expression evaluation

Conditional Statements and Control Structures

• if/else: Executes different code blocks based on a condition
• switch: Provides a more concise way to handle multiple conditions
• for loop: Iterates a block of code a specific number of times
• while loop: Repeats a block of code as long as a condition is true

PHP Functions

• Defining Functions:
  • Functions encapsulate blocks of code for reuse
  • They improve code organization and readability
• Return Values:
  • Functions can return values using the return keyword
• Passing Arguments:
  • Functions can accept input values as arguments

PHP Arrays

• In PHP, the array() function is used to create an array

PHP Arrays: Types

• Indexed Arrays:
  • Arrays store collections of data
  • Indexed arrays use numerical keys
• Associative Arrays:
  • Associative arrays use string keys to access values
• Multidimensional Arrays:
  • Multidimensional arrays can store arrays within arrays

Dumping an Array

• To show PHP data and debug, use print_r() or var_dump()

Building Up an Array

• New items can be added in an array using a key

Looping Through an Array

Counted Looping Through an Array

Array Functions

• array_key_exists($key, $ar) returns TRUE if key is set in the array
• isset($ar['key']) returns TRUE if key is set in the array
• count($ar) returns how many elements are in an array
• is_array($ar) returns TRUE if a variable is an array
• sort($ar) sorts the array values (loses key)
• ksort($ar) sorts the array by key
• asort($ar) sorts array by value, keeping key association
• shuffle($ar) shuffles the array into random order

HTTP and PHP Arrays

HTTP

• HTTP (Hypertext Transfer Protocol) is the foundation of communication on the web
• It is a request-response protocol used by web browsers (clients) and web servers

HTTP Methods

• GET - Requests data from a server (e.g., visiting a webpage)
• POST - Sends data to a server (e.g., submitting a form)
• PUT - Updates existing data
• DELETE – Removes data

Interacting with HTTP Requests

• PHP arrays interact with HTTP requests, for example, $_GET and $_POST

HTTP Requests and PHP Arrays

• Use superglobal arrays $_GET and $_POST to handle data sent via HTTP requests
• $_GET for when data is sent through the URL query string
• The data is visible in the URL