PHP and Dynamic Web Pages

PHP Overview

• Covers how to embed PHP within HTML for dynamic content creation and client-server communication
• Explores PHP's integration with HTML, CSS, and databases like MySQL
• PHP is essential for creating dynamic, database-driven websites
• Understanding PHP's interaction with HTML, CSS, and databases is vital for web development, cybersecurity, and software engineering

Learning Objectives

• Analyze basic PHP features
• Create a webpage with PHP
• Summarize the use of GET and POST methods
• Create web forms with PHP and HTML

PHP Basics

• Hypertext Preprocessor (PHP) is a server-side scripting language for web development
• PHP code is embedded within HTML to create dynamic content
• PHP scripts execute on the server before rendering content in the browser
• Client-side programming executes in browser, dynamic webpages use Javascript
• Server-side executes on the web server, languages include PHP, NodeJS, Python, and Tomcat (Java)

Using PHP

• PHP is a server-side language that generates HTML for web browsers
• PHP filenames must end with .php
• PHP code is integrated directly into HTML
• tag is used to start PHP code and to end PHP code
• The echo keyword outputs a value to the browser
• time() function returns the current time in the number of seconds since the Unix Epoch
• PHP statements end with a semicolon
• Browser only recieves HTML from the server. The PHP remains unseen

Comments in PHP

• PHP comments provide information about the code or disable code execution
• // and # are used for single-line comments
• `` are used for multiple-line comments

Variables

• PHP variables are containers for storing information
• Variables store info and allow data manipulation within a program
• Variables are automatically assigned a data type
• Variable names always start with a $ (e.g., $age)
• A name must start with a letter or underscore
• A name cannot start with a number
• A name can only contain alpha-numeric characters and underscores (A–z, 0–9, and _)
• Variable names are case-sensitive ($age and $AGE are different variables)
• Strings must have quotes, other data types do not need quotes

Functions

• PHP has functions that take inputs (arguments) and perform specific tasks
• Functions return a value that can be stored in a variable or display results directly to the browser
• PHP has over 1,000 built-in functions for specific tasks
• You can create your own functions: a block of code that can be used repeatedly
• Is not executed automatically, but upon a function call

Function Arguments

• Information is passed to functions through arguments, specified after the function name inside parentheses

Returning Functions

• Use the return statement to return a value from a function
• String operator dot (.) is used to concatenate strings

The var_dump Function

• var_dump() outputs a variable's value and data type
• Useful when the data type or value is unknown

Echo and Print

• echo and print are used to produce output using PHP
• echo is more commonly used due to its speed and flexibility

PHP Constants

• A constant is an identifier (name) for a simple value that cannot be changed
• define() function is used to create a constant
• Format: define(name, value, case-insensitive)
  • name specifies the name of the constant
  • value specifies the value of the constant
  • case-insensitive specifies whether the constant name should be case-insensitive (default is false)

The Equal Operator

• Equal operator (==) checks that the values match
• Triple equal operator (===) checks that the values and datatypes match

If...Else Statement

• PHP supports if statements like most programming languages

ElseIf Statement

• elseif statements are used when an if statement needs more than two outcomes
• There can be many elseif statements
• The else statement is optional but must be at the end

Combining Conditions

• Logical operators combine and evaluate conditions
• Common logical operators include "and" (&&), "or" (||), "xor", and "not" (!)

Loops

• Loops allow repeating a block of code multiple times

Joining Strings

• Strings can be joined using the + operator (adds data types together) or the . operator (concatenates data types)

PHP Quotes

• PHP allows using double quotes ("a") or single quotes ('a') for strings
• Double quotes convert escape sequences and replace variables with their values
• Double quotes should be used in general

Create an Array in PHP

• The array() function is used to create an array
• Three types of arrays: indexed, associative, and multidimensional

Indexed Arrays

• Each element is assigned a numeric index, starting at 0

Associative Arrays

• Arrays use named keys (strings) that are assigned to them

Multidimensional Arrays

• An array contains one or more arrays
• PHP supports arrays that are two, three, four, five or more levels deep

Creating Online Forms

• PHP is used to receive data from users via forms

URL Parameters

• URL parameters (query or GET parameters) are key-value pairs appended to the end of a URL
• Allow clients to pass additional data to the server, often for filtering, sorting, and pagination purposes
• The query string contains a set of key-value pairs separated by an ampersand (&)

Isset Function

• isset() function is used to test if a variable has been assigned a value
• Used to make sure that users have provided data and prompt them if not

GET and POST

• GET and POST create an array
• Forms data is accessed Using $_GET Or $_POST
• These are superglobals, accessible regardless of scope

$_GET

• GET is an array of variables passed to the current script via URL parameters
• Visible to everyone
• Information is limited to about 2,000 characters
• Should be used for sending non-sensitive data

$_POST

• POST is an array of variables passed to the current script via the HTTP POST method
• Invisible variable values for others
• No limits on the amount of information to send
• Can not bookmark page

Creating Forms

• Forms use the `` tag
• The method attribute specifies the HTTP method (GET or POST)
• The action attribute refers to the URL of the PHP script
• The `` element is used to collect data from the user
• ProcessName.php produces hello output if name is set, or "You did not provide a name"

Checkboxes

• Uses the `` tag
• Checkboxes send no data if not checked
• Two possibilities: checked (value "On" is sent) or not checked (no data is sent)

Radio Buttons

• Allows single selection of many choices
• The tag displays a radio button
• Can show the user a picture of their selected button by including the image into the value parameter of a radio button

Step One: Create the Header File

• Can create separate file for top portion of the code
• Allows for code to be reused
• Created using PHP file within HTML tags

Step Two: Create the Footer File

• Can create a separate file for the footer, since the footer rarely changes
• Use PHP file within HTML tags

Step Three: Create the Main File

• The main file includes the header and footer files
• `` is used to include the header and footer
• Can duplicate pages and make changes

Step Four: View Results

• Deploy the pages on the latcs6 server to view results in a browser
• Access via http://webprog.cs.latrobe.edu.au/~username

Synchronous Practice Class Tasks

• Task 1: Copy an existing page (e.g., page1.html) to create a new page (page2.php)
• Task 2: Design a form input with text boxes () and a dropdown menu ()
• Task 3: Copy processOrder.php into the lab 6 directory
• Task 4: Open page2.php in a browser, enter data, and click submit
• Task 5: Add a hyperlink () on processOrder.php to return to the homepage (page1.html)
• Task 6: Calculate the total price based on user input
• Task 7: Apply a 10% discount if the customer has a coupon code of 10%2018
• Task 8: Show a picture of the purchased item using images copied into the fruitpics directory
• Task 9: Improve the appearance of processOrder.php by applying the same HTML from other pages

Week In Review

• PHP can be use to create webforms to collect data from clients