Web Tech Unit 2: PHP Basics

PHP Basics

• PHP generates dynamic page content, allowing for real-time updates and interactions.
• Capable of file management: create, open, read, write, delete, and close files on the server.
• Collects form data and sends/receives cookies for user sessions.
• Manages database operations, including adding, deleting, and modifying data.
• Controls user access and can encrypt data for security purposes.

PHP File Characteristics

• PHP files include a mix of text, HTML, CSS, JavaScript, and PHP code.
• PHP code executes on the server, returning results as plain HTML to the browser.
• PHP files have the extension ".php".

Variable Declaration in PHP

• No explicit command to declare a variable; created on first value assignment.
• Single dollar sign ($var) denotes a normal variable.
• Double dollar sign ($$var) indicates a reference variable, storing the value of another variable.

Data Types and Functions

• The var_dump() function returns data type and value:
  • Examples include integers (5), strings ("John"), floats (3.14), booleans (true), arrays ([2, 3, 56]), and NULL values.

Constants in PHP

• Define constants using define(name, value, case-insensitive).
• Example: define("GREETING", "Welcome to PHP!"); allows use in functions.
• Constants are globally scoped and can also be created using the const keyword: const MYCAR = "Volvo";.

PHP Data Types

• Strings: Defined with double quotes (") or single quotes (').
• Integer: Whole numbers, e.g., $x = 5985;.
• Float: Decimal numbers, e.g., $x = 10.365;.
• Boolean: Represents truth values, e.g., $x = true;.
• Array: Collection of values, e.g., $cars = array("Volvo", "BMW", "Toyota");.
• NULL: Represents a variable without a value, e.g., $x = null;.

Variable Scope

• Global Scope: Variables outside functions can only be accessed externally. Example shows access error if accessed internally.
• Local Scope: Variables declared inside functions are local and inaccessible from outside.

Conditional Statements

• PHP supports if, else, and switch statements for decision-making.
• if statement example: if (5 > 3) { echo "Have a good day!"; }
• switch statement allows multi-case checks, default executing if no cases match.

Superglobals

• Superglobals are automatically accessible throughout the PHP code, requiring no declarations.
• Common superglobals include:
  • $_GET: Retrieves variables from the HTTP GET method.
  • $_POST: Retrieves variables from the HTTP POST method.
  • $_SERVER, $_REQUEST, and $_GLOBALS access server variables and global values.