COMP721 Web Development - PHP Part 1 Notes

PHP Basics

  • Basic PHP Scripts
    • Getting started with PHP
    • Understanding PHP data types and operators
    • Floating-point precision issues
    • Expressions, including the Euclidean Algorithm (GCD)
    • Functions and control structures

Web Development Environment

  • Components needed for PHP development
    • A web browser (e.g., Chrome, Firefox, Edge, Safari)
    • A web server (e.g., Apache with PHP support)
    • A database (e.g., MySQL, MariaDB)
    • Recommended IDE: VS Code
    • Stack options include WAMP, MAMP, LAMP, XAMPP

PHP Overview

  • PHP: Stands for PHP Hypertext Preprocessor
  • Examples of other acronyms: GNU (GNU is Not Unix), PIP (PIP Install Packages)

Running PHP

  • On personal devices, you can set up an AMP stack (Apache, MySQL, PHP) using WAMP, MAMP, LAMP, or XAMPP
  • Online PHP editors are available for quick testing

Embedded Scripting

  • PHP can be embedded in HTML documents
  • Server-side scripts (e.g., PHP, C#) are executed on the server and not sent to the client
  • Client-side languages (e.g., JavaScript) run in the user's browser

PHP Files

  • PHP files should have a .php extension
  • PHP code is executed on the server, and the output is sent to the client

Code Blocks in PHP

  • Code Declaration Blocks: Sections for PHP code
    • Standard PHP script delimiters: <?php ... ?>
    • Short tags: <? ... ?> are not recommended
    • ASP-style delimiters: <% ... %>

Functions in PHP

  • A function is a self-contained block of code designed to perform a specific task.
    • Functions are invoked with their name and can accept parameters: function_name(argument1, argument2)
    • Example of a basic function:
      php function greet($name) { echo "Hello, $name!"; } greet("John");
  • The phpinfo() function displays configuration information about PHP.

Output in PHP

  • Use echo and print to send output back to the client:
    • Example:
      php echo "Welcome to PHP!";

Variables in PHP

  • Variables must start with a $ sign, followed by the identifier name

  • Variable naming guidelines:

    • Can include letters, numbers, or underscores
    • Cannot begin with a number or contain spaces

  • Example:
    ```php
    $votingAge = 18;
    echo $votingAge; 

## Data Types in PHP  

- **Primitive Data Types**:  
  - **Integers**: Whole numbers, e.g., `-1`, `0`, `5`  
  - **Floats**: Decimal numbers, e.g., `3.14`  
  - **Booleans**: `true` or `false`  
  - **Strings**: Sequences of characters  

## Arrays  

- **Indexed Arrays**: Collections of values stored with numerical indexes  
- **Associative Arrays**: Arrays that use named keys instead of numeric indexes  
- Example of accessing an array:

php
$fruits = array("apple", "banana", "cherry");
echo $fruits[1];
```

PHP Expressions

  • An Expression is a combination of variables, literals, and operators that PHP can evaluate.
  • Operators Types:
    • Arithmetic Operators: +, -, *, /, %
    • Assignment Operators: =, +=, -=, etc.
    • Comparison Operators: ==, ===, !=, etc.
    • Logical Operators: &&, ||, !

Control Structures

  • Functions: Used to encapsulate code for reuse. Defined using function_name(parameters) { ... }
  • Conditionals: if, else, and switch statements control program flow
  • Loops: Repeats code blocks while a condition is true, includes while, for, and foreach structures

Summary

  • These are the foundational concepts of PHP programming essential for creating dynamic web applications.