PHP Arrays: Indexed and Associative

• PHP Arrays are data structures storing multiple similar-type elements in a single variable.
• Arrays are accessed using their index number or key.
• PHP array functions enable interaction and manipulation of array elements.

PHP Array Types

• Indexed arrays contain a numeric index.
• Associative arrays have named keys.
• Multidimensional arrays contain one or more arrays.

Indexed Arrays

• An array can store multiple values in one single variable.
• To access an array item, refer to the index number.
• To change an array item's value, use the index number.
• A foreach loop prints the values of an indexed array.
• The key of an indexed array is a number, starting at 0 by default.
• Using the array_push() function adds a new item, assigning the next available index.

Associative Arrays

• Associative arrays use named keys.
• An array item can be referenced by its key name.
• Values in associative arrays can be changed by referring to their key.
• A foreach loop can print all values of an associative array.

Multidimensional Arrays

• A multidimensional array contains one or more arrays.
• The dimension indicates the number of indices needed to select an element.
• Two indices are needed for a two-dimensional array.
• Three indices are needed for a three-dimensional array.
• Two-dimensional arrays are arrays of arrays.
• A two-dimensional $nba array contains four arrays, accessed by two indices, row and column.
• To access elements, point to the two indices (row and column).
• Nested for loops can be used to get elements.

PHP Forms

• PHP/HTML forms send user information to the server and return results to the browser.
• Forms collect user information for client-side or server-side validation.
• The <form> tag creates a form.
• Form controls facilitate communication between client and server.
• Textbox: Used for single-line input (e.g., names).
• Textarea: Used for multi-line input (e.g., addresses).
• Dropdown: Allows selection from a list of values.
• Radio Buttons: Used to select one option from a set.
• Checkbox: Used to select multiple options.
• Buttons: Clickable controls used to submit the form.

Form Validation

• Validation ensures that the user provides relevant information.
• Basic validation can be done using HTML elements (e.g., setting type as "email" for email input).
• All form fields should have a required attribute preventing empty submissions.

PHP Form Processing

• When a form is submitted, it's processed similarly to the example provided.
• The HTML script is rewritten to validate all form fields.
• If there are no errors, the received information is displayed in a tabular form.

PHP Form Handling

• The PHP superglobals $_GET and $_POST collect form data.
• After a form is submitted, the data is sent to a PHP file named "welcome.php" using the HTTP POST method.
• Submitted data can be displayed by echoing all the variables.

PHP Methods and Arrays Used in Form Processing

• isset() determines if a variable or form control has a value.
• $_GET[] retrieves information from the form control via URL parameters, and takes the attribute given in the URL as the parameter.
• $_POST[] retrieves information from the form control via the HTTP POST method, and takes the name attribute of the corresponding form control as the parameter.
• $_REQUEST[] retrieves information while using a database.

ITEC 106 GET vs. POST

• Both GET and POST create key/value pair arrays.
• The arrays hold the names of the form controls as keys and the input data as values.
• Both are treated as $_GET and $_POST, which are superglobals accessible from any function, class, or file.

When to use GET?

• Information sent via GET is visible in the URL.
• There is a 2000-character limit.
• It is useful for bookmarking pages.
• GET should never be used for sensitive data like passwords.

When to use POST?

• Information sent via POST is not visible in the URL.
• There are no limits on the information sent.
• POST supports advanced functionality such as file uploads.
• The same example can use the GET method instead of POST.
• Bookmarking the page is not possible since variables are not displayed in the URL.

ITEC 106 PHP Global Variables - Superglobals

• Superglobals are predefined variables in PHP that are always accessible.
• PHP superglobal variables include: $GLOBALS, $_SERVER, $_REQUEST, $_POST, $_GET, $_FILES, $_ENV, $_COOKIE, $_SESSION.
• $GLOBALS is an array containing all global variables.
• Global variables can be accessed from any scope.
• To use a global variable inside a function, define it with the global keyword or use the $GLOBALS syntax.
• $_SERVER holds information about headers, paths, and script locations.
• $_REQUEST contains submitted form data and cookie data and is an array combining data from $_GET, $_POST, and $_COOKIE.
• Access data using $_REQUEST['field_name'].
• $_POST contains variables received via the HTTP POST method.
• Two main ways to send variables:
  • HTML forms
  • JavaScript HTTP requests
• $_GET contains variables received via the HTTP GET method.
• Two main ways to send variables:
  • Query strings in the URL
  • HTML Forms

Cookies

• A cookie identifies a user and is a small file embedded on the user's computer.
• Each time the same computer requests a page, it sends the cookie.
• A cookie is created with the setcookie() function.
• To create a cookie named "user" with the value "John Doe" that expires after 30 days, setcookie("user", "John Doe", time() + (86400 * 30), "/"); can be used
• This creates a cookie named "user" with the value "John Doe" that expires after 30 days.
• The / means the cookie is available across the entire website.
• To retrieve a cookie value, $user = $_COOKIE['user']; can be used
• To check if the cookie is set, if (isset($_COOKIE['user'])) can be used

PHP Sessions

• A session stores data on the server instead of the user's computer.
• Each session has a unique identifier called Session ID (SID) to link the user with the information.
• Cookies can be modified by users, making them vulnerable to attacks which makes sessions advantageous over cookies.
• Cookies are sent with every request, which can slow down the site which makes sessions advantageous over cookies.
• The session_start() function begins a session: session_start();
• Storing session data involves storing data in key-value pairs using the $_SESSION[] superglobal array: $_SESSION['key'] = 'value';
• Accessing stored data is done by calling session_start() and using the key: $value = $_SESSION['key'];
• Deleting specific session data involves using: unset($_SESSION['key']);
• Use session_destroy() to completely destroy a session: session_destroy();
• Session IDs are randomly generated by PHP.
• Session data is stored on the server, so it doesn't need to be sent with every request.
• Call session_start() at the beginning of the page, before any output.

PHP Casting

• Type casting a variable in PHP converts it from one data type to another.
• It ensures consistent behavior and accurate calculations.

Casting in PHP is done using the following statements:

• (string) converts to String
• (int) converts to Integer
• (float) converts to Float
• (bool) converts to Boolean
• (array) converts to Array
• (object) converts to Object
• (unset) converts to NULL

Examples of Casting

• Casting to String: $string = (string) $value;
• Casting to Integer: $integer = (int) $value;
• Casting to Boolean: If a value is 0, NULL, false, or empty, it converts to false; otherwise, true.
• Casting to Float: $float = (float) $value;
• Casting to Array: $array = (array) $value;
  • Most data types convert into an indexed array with one element.
• Casting to Object: $object = (object) $value;
  • Most data types convert into an object with one property named "scalar".
• Casting to NULL: $nullValue = (unset) $value;

PHP Strings

• string is a series of characters.
• PHP supports various data types, including strings.
• Strings can be created using either double or single quotation marks:
  • Example: $string1 = "Hello, World!"; or $string2 = 'Hello, World!';
• Alphanumeric characters are allowed in string variables.
• Double quoted strings perform actions on special characters.

PHP String Functions

• strtoupper(): Converts all characters in a string to upper case.
  • Syntax: strtoupper($string)
• ucfirst(): Converts the first character of a string to upper case, leaving the rest unchanged.
  • Syntax: ucfirst($string)
• lcfirst(): Converts the first character of a string to lower case, leaving the rest unchanged.
  • Syntax: lcfirst($string)
• ucwords(): Converts the first character of every word in a string to upper case.
  • Syntax: ucwords($string)
• strlen(): Returns the length of a string, including whitespaces and special characters.
  • Syntax: strlen($string)

PHP Operators

• Operators are used to perform operations on variables and values.
• PHP divides operators into the following groups:
  • Arithmetic operators: Used with numeric values for operations like addition, subtraction, multiplication, etc.
  • Assignment operators: Used to assign values to variables.
  • Comparison operators: Used to compare two values (numbers or strings).
  • Increment/Decrement operators: Used to increase or decrease a variable's value.
  • Logical operators: Used to combine conditional statements.
  • String operators
  • Array operators
  • Conditional assignment operators

Conditional Statements in PHP

• Types of conditional statements:
  • if statement: Executes a block of code if a condition is true.
    • Syntax: if (condition) { code to execute; }
    • else statement: Executes a block of code if the preceding if statement is false.
      • Syntax: else { code to execute; }
    • else if statement: Evaluates multiple conditions sequentially.
      • Syntax: elseif (condition) { code to execute; }
    • switch statement: Tests a variable against multiple values.
      • Syntax: switch (variable) { case value1: code to execute; break; case value2: code to execute; break; default: code to execute; }

PHP Loops

• Types of loops:
  • while loop: Executes a block of code as long as a condition is true.
    • Syntax: while (condition) { code to execute; }
  • do...while loop: Executes a block of code at least once, then repeats while a condition is true.
    • Syntax: do { code to execute; } while (condition);
  • for loop: Executes a block of code a specified number of times.
    • Syntax: for (initialization; condition; increment) { code to execute; }
  • foreach loop: Loops through each element in an array or each property in an object.
    • Syntax: foreach (array as value) { code to execute; } or foreach (array as key => value) { code to execute; }

PHP Functions

• A function is a block of code designed to perform a specific task.
• Functions take parameters, execute statements, and return results.

Types of Functions

• Built-in functions: A large collection of pre-coded functions provided by PHP.
• PHP has many built-in functions like var_dump(), fopen(), print_r(), gettype().
• User-defined functions: PHP allows the creation of custom functions.

Creating a Function

• A function name ends with parentheses ().
• It starts with the keyword function.
• Function Syntax Example
• function functionName($param1, $param2){ //code to be executed }
• Parameter Passing to Functions -PHP allows two ways to pass arguments to functions: -Pass by Value -Pass by Reference Syntax Example
• function functionName(&$param)
• PHP stands for PHP: Hypertext Preprocessor.
• Used for server-side scripting, designed for web development.
• PHP is open-source and easy to learn.
• PHP syntax defines how PHP code is structured.
• PHP scripts can be mixed with HTML.
• PHP files are saved with the.php extension.

PHP Versions

• Introduced by Rasmus Lerdorf in 1993.
• PHP code is executed on the server.
• It Can integrate with databases (e.g., MySQL or PostgreSQL).
• Supports protocols like HTTP, IMAP, and FTP.
• Websites like Facebook and Yahoo are built using PHP.
• PHP can be embedded in HTML, allowing dynamic content generation.
• File extension is .php.
• Output displays as ITEC

Escaping into PHP

• There are a few various code examples on how to insert PHP into HTML
• The shortest option is SGML or Short HTML Tags which: -Starts with -Requires short_open_tag