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PHP - Help Understanding Abstract Class
Can someone help me understand this code...
Quote abstract class FormCollection{ protected $fields = $_POST; protected $validator; protected function __construct($validator){ $this->validator = $validator; } } Questions: ---------------- 1.) If an Abstract Class cannot be instantiated, then how can there be Properties? 2.) I guess $fields is supposed to be an array? How do I know that? Isn't there a way to do "type hinting" or whatever? 3.) What data-type is $validator? TomTees Similar TutorialsI can't find an explicit answer on this anywhere, but when you create a child class from an abstract class must you use ALL of the methods that are inside the abstract class in the new child class? Or are these methods just available to the child class to pick and choose?
I am seriously trying to wrap my head around abstract classes, but the more I try to understand it the more I get confused.
I've even dug out a book by Larry Ullman to no avail.
Here's the example in the book:
Shape abstract class
<?php # Script 6.1 - Shape.php
/* This page defines the Shape abstract class.
* The class contains no attributes.
* The class contains to abstract methods.
* - getArea()
* - getPerimeter()
*/
abstract class Shape {
// No Attributes to declare.
// No constructor or destructor defined here.
// Method to calculate and return the area.
abstract protected function getArea();
// Method to calculate and return the perimeter.
abstract protected function getPerimeter();
} // End of Shape Class.
Triangle class:
<?php # Script 6.2 - Triangle.php
/* This page defines the Triangle class.
* The class contains two attributes:
* - private $_sides (array)
* - private $_perimeter (number)
* The class contains three methods.
* - __construct()
* - getArea()
* - getPerimeter()
*/
class Triangle extends Shape {
// Declare the attributes:
private $_sides = array();
private $_perimeter = NULL;
// Constructor:
function __construct($s0 = 0, $s1 = 0, $s2 = 0) {
// Store the values in the array:
$this->_sides[] = $s0;
$this->_sides[] = $s1;
$this->_sides[] = $s2;
// Calculate the perimeter:
$this->_perimeter = array_sum($this->_sides);
} // End of constructor.
// Method to calculate and return the area:
public function getArea() {
// Calculate and return the area:
return (SQRT(
($this->_perimeter/2) *
(($this->_perimeter/2) - $this->_sides[0]) *
(($this->_perimeter/2) - $this->_sides[1]) *
(($this->_perimeter/2) - $this->_sides[2])
));
} // End of getArea() method.
// Method to return the perimeter:
public function getPerimeter() {
return $this->_perimeter;
} // End of getPerimeter() method.
} // End of Triangle Class.
and to execute in finding the area and perimeter of a triangle:
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Abstract Class</title>
</head>
<body>
<?php # Script 6.3 - abstract.php
// This page uses the Triangle class - (Script 6.2), which is derived from Shape (Script 6.1)
// load the class definitions:
require('Shape.php');
require('Triangle.php');
// Set the triangle's sides:
$side1 = 5;
$side2 = 10;
$side3 = 13;
// Print a little introduction:
echo "<h2>With sides of $side1, $side2, and $side3...</h2>\n";
// Create a new triangle:
$t = new Triangle($side1, $side2, $side3);
// Print the area.
echo '<p>The area of the triangle is ' . $t->getArea() . '</p>';
// Print the perimeter.
echo '<p>The perimeter of the triangle is ' . $t->getPerimeter() . '</p>';
// Delete the object:
unset($t);
?>
</body>
</html>
What is the point of having an abstract class when it runs fine without it being declared? For example I can take out extends Shape in the Triangle class and it will work just fine? I don't know if If I will ever understand this concept of abstract and interface classes....
Any help in this matter will be greatly appreciated. Thanks John
OK, I fooled around with it some more and took out the include('Shape.php') and it spat an out an error stating it wasn't found. So is an abstract class just forcing a person to adhere to the methods being declared in the abstract class? (I'm probably not explaining this right).
Edited by Strider64, 03 October 2014 - 10:55 AM. Would someone help me out with Abstract Classes and Interfaces... Some questions... 1.) When you have an Interface with Methods, then any Concrete Class that "implements" said Interface must include all of the listed Methods, correct? 2.) When you have an Abstract Class with Properties & Methods, are you required to use all of the listed Properties & Methods similar to how an Interface works? 3.) What is the intent of using Abstract Classes vs. Interfaces? TomTees I was given the snippet below and am trying to figure some things out... abstract class FormCollection{ protected $fields = $_POST; protected $validator; protected function __construct($validator){ $this->validator = $validator; } // and so on... } class RegistrationForm extends FormCollection{ private $formInputs = array(); // and so on... } Questions: ----------------- 1.) If I instantiate the concrete class, RegistrationForm, like this... $form = new RegistrationForm(new Validator()); What does that do to the abstract class, FormCollection? Is it getting instantiated too? 2.) I thought you could NOT instantiate an abstract class like FormCollection? 3.) If you can't, then why is there a constructor in the abstract class like FormCollection? 4.) This code seems wrong... protected $fields = $_POST; I was told by somene that PHP doesn't allow you to assign values to a class method at compile time unless the values come from a constant?! TomTees I've been searching high and low for some decent (actually, they can be crap, just be REAL) real-world examples of uses of abstract classes and interfaces. I've seen many design patterns, and I get the concept, but now I need to put them into practice. And I gotta say, I'm absolutely sick of class Animal, class Dog extends Animal, class Vehicle, class Van extends Vehicle examples. Those are CRAP for illustrating real uses of the functionality given to us by OOP. It's one thing to teach a concept, and it's another to put into use within a real application. I can only find the former and the not the latter. Does anyone have any links to, or can they post their own examples of, abstract classes and interfaces in use? I have mysqli object in Database class base: [color=]database class:[/color] class Database { private $dbLink = null; public function __construct() { if (is_null($this->dbLink)) { // load db information to connect $init_array = parse_ini_file("../init.ini.inc", true); $this->dbLink = new mysqli($init_array['database']['host'], $init_array['database']['usr'], $init_array['database']['pwd'], $init_array['database']['db']); if (mysqli_connect_errno()) { $this->dbLink = null; } } } public function __destruct() { $this->dbLink->close(); } } Class derived is Articles where I use object dBLink in base (or parent) class and I can't access to mysqli methods (dbLink member of base class): Articles class: require_once ('./includes/db.inc'); class Articles extends Database{ private $id, .... .... $visible = null; public function __construct() { // Set date as 2009-07-08 07:35:00 $this->lastUpdDate = date('Y-m-d H:i:s'); $this->creationDate = date('Y-m-d H:i:s'); } // Setter .... .... // Getter .... .... public function getArticlesByPosition($numArticles) { if ($result = $this->dbLink->query('SELECT * FROM articles ORDER BY position LIMIT '.$numArticles)) { $i = 0; while ($ret = $result->fetch_array(MYSQLI_ASSOC)) { $arts[$i] = $ret; } $result->close(); return $arts; } } } In my front page php I use article class: include_once('./includes/articles.inc'); $articlesObj = new articles(); $articles = $articlesObj->getArticlesByPosition(1); var_dump($articles); [color=]Error that go out is follow[/color] Notice: Undefined property: Articles::$dbLink in articles.inc on line 89 Fatal error: Call to a member function query() on a non-object in articles.inc on line 89 If I remove constructor on derived class Articles result don't change Please help me I have an existing instance of my class Database, now I want to call that instance in my Session class, how would I go about doing this? Ok. I know you can pass the object of a class as an argument. Example: class A { function test() { echo "This is TEST from class A"; } } class B { function __construct( $obj ) { $this->a = $obj; } function test() { $this->a->test(); } } Then you could do: $a = new A(); $b = new B($a); Ok so that's one way i know of. I also thought that you could make a method static, and do this: (assuming class A's test is 'static') class B { function test() { A::test(); } } But that is not working. I'd like to know all possible ways of accomplishing this. Any hints are appreciated. thanks If a class has a constructor but also has a static method, if I call the static method does the constructor run so that I can use an output from the constructor in my static method? --Kenoli Hi Can you call Class A's methods or properties from Class B's methods? Thanks. Hi, I need to be able to call a class based on variables. E.G. I would normally do: Code: [Select] $action = new pattern1() but i would like to be able to do it dynamicaly: Code: [Select] $patNum = 1; $action = new pattern.$patNum.() Im wondering if that's possible? If so what would the correct syntax be? Many Thanks. I'm attempting to convert a huge project I made with mysql to PDO. I have many cases where I would use a WHILE statement to return a query array. Code: [Select] while($row= mysql_fetch_array($result)){From what I've seen so far, it looks as though I need to use a foreach statement to do the same task. Code: [Select] foreach ($dbh->query($sql) as $row){ Is that correct? I have a system that I want to change. Hi, can someone help me figure out why the logo div isn't centering? Code: [Select] <?php require_once("functions.php"); ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Untitled Document</title> <style type="text/css"> td { border-top-style: solid; border-right-style: solid; border-bottom-style: solid; border-left-style: solid; border-top-color: #30C; border-right-color: #30C; border-bottom-color: #30C; border-left-color: #30C; } </style> <link href="doggyTreats.css" rel="stylesheet" type="text/css" /> </head> <body> <?php [color=yellow]logo();[/color] navBar(); echo "<div id=\"mainContent\">"; echo "<form action=\"\" method=\"post\" name=\"catalog\">"; DatabaseConnection(); $query = "SELECT * FROM treats"; $result_set = mysql_query($query) or die(mysql_error()); $i = 0; echo "<table>"; while ($row = mysql_fetch_array($result_set)) { echo"<tr><td width=\"2s00px\"><img src=\"{$row['product_pic']}\" /></td><td width=\"200px\">{$row['product_title']}.<br /><br />{$row['product_Description']}.<br /> Price: \${$row['price']}.<br /><br />Quantity <input name=\"quantity\" type=\"text\" size=\"2\" /></td></tr>"; } echo "<tr>"; echo "<td><input name=\"submit\" type=\"button\" value=\"Proceed to Checkout\" />"; echo "</table>"; echo "</form>"; echo "</div>"; footer(); ?> </body> </html> Code: [Select] #navBar { background-color: #060; width: 200px; padding-top: 50px; padding-bottom: 250px; float: left; } #navBar #menu { margin-right: 6px; } .menuOption { background-image: url(assets/bone2a.gif); background-repeat: no-repeat; padding-bottom: 25px; list-style-type: none; height: 20px; padding-top: 26px; text-align: center; } body { background-color: #0089cc; }[color=yellow] #logo { text-align: center; margin-top: 5px; height: 123px; width: 182px; }[/color] #footer { font-style: italic; text-align: center; } .shoppingCart tr th { padding: 5px; } .shoppingCart tr td { padding: 5px; } #mainContent { width: 350px; margin-top: 30px; } Code: [Select] <?php [color=yellow]function logo() { echo "<div id=\"logo\">"; echo "<img src=\"assets/logo.gif\" alt=\"logo\" />"; echo "</div>"; }[/color] function footer() { echo "<div id = \"footer\">"; echo "Auntie Vic\'s Treatery <br />"; echo "PO Box 34092 <br />"; echo "Clermont, IN 46234 <br />"; echo "317-701-0343 <br />"; echo "<a href=\"mailto:auntievics@gmail.com\">Email Us</a>"; echo "</div>"; } function navBar() { echo "<div id = \"navBar\">"; echo "<ul id=\"menu\">"; echo "<li class=\"menuOption\"><a href=\"index.html\">Home</a></li>"; echo "<li class=\"menuOption\"><a href=\"aboutUs.html\">Management Team </a></li>"; echo "<li class=\"menuOption\"><a href=\"treats.html\">Treats </a></li>"; echo "<li class=\"menuOption\"><a href=\"charities.html\">Supported Charities</a></li>"; echo "<li class=\"menuOption\"><a href=\"order.html\">Orders</a></li>"; echo "</ul>"; echo "</div>"; } ?> Hi All I have a basic login system on my site. How would I go about displaying the current logged in user information from the session Id. its quite confusing..... <?php require 'Mysql.php'; class Membership { function validate_user($un, $pwd) { $mysql = New Mysql(); $ensure_credentials = $mysql->verify_Username_and_Pass($un, ($pwd)); if($ensure_credentials) { $_SESSION['status'] = 'authorized'; header("location: ../selfbuild/Controlpanel.php"); } else return "Please enter a correct username and password"; } function log_User_Out() { if(isset($_SESSION['status'])) { unset($_SESSION['status']); if(isset($_COOKIE[session_name()])) setcookie(session_name(), '', time() - 1000); session_destroy(); } } function confirm_Member() { session_start(); if($_SESSION['status'] !='authorized') header("location: login.php"); } } Just need to display the user name at the moment but am kinda not getting how its done. Do I just need <?php session_start(); echo $un Let's see.... You add values to variables but you can declare them before assigning a value... Loops are great - they do things until a specific criteria is met....then I exit or break out of them. Functions are code that do specific tasks (or series of tasks) & can be called upon at any given time during a script. An array is like a....hotel with many different rooms - each room being a different value. I get GET and POST...and know how to use them between pages. Sessions can be used to pass data between pages - they help to keep track of things.... Cookies are like little signatures from your script that you can give to a users browser for any number of reasons. I guess you could say I'm starting to get it. It's only been 4 months. That being said can someone give me a brief and yet simple summary of what a PHP Class is... Hello, After a user gets input into my Users table in my database, I'm using lastInsertId() to grab the newly created ID and then enter the newly created ID (along with some other stuff) into a separate table. Could this potentially be a problem? In other words, what happens if 2 users on 2 different computers both sign up a the same time? How will be database know which lastInsertId() to use? Here's my current code: $dbWrite->insert('users', $data); $last_id = $dbWrite -> lastInsertId(); // get the ID that was just created $data = array ('course_id' => $_POST['course_id'], 'user_id' => $last_id); $dbWrite->insert('course_enrollment', $data); // Use that new ID in a different table Perhaps there's a way to combine the steps? Thank you for your thoughts... Can someone explain to me in plain English what is the purpose of imagecreatefromgif?? I read the Manual but am not really understanding what purpose it servers in the larger image rendering process. Also, how should I Error-Handle this function - if at all?! Thanks, Debbie I need some help understanding the below syntax (the ? and the colon are throwing me) isset($_POST['cardType']) ? $_POST['cardType'] : ''; Thanks for any help on this .. Frank Hi.
I've been trying to understand the concept of password_hash but so far it has eluded me!
registration
<?php
if(isset($_POST['submit'])){
$name = $_POST['name'];
$email = $_POST['email'];
$password = $_POST['password'];
//$pass_hash = PassHash::hash($_POST['password']);
$hash = password_hash($password, PASSWORD_BCRYPT);
$stmt = $pdo->prepare("INSERT INTO hash_test(name, email, password) VALUES(:name, :email, :password)");
$stmt->execute(array(
':name' => $name,
':email' => $email,
':password' => $hash
));
if ($stmt->rowCount() ==1){
echo "Registration Successful";
}else{
echo "There was a problem taking your request";
}
}
?>
The registration is working fine and all fields are inserted. The problem is when loggin in, its giving me an error : unknown variable which is the $hash. The verify parameter is thus:
password_verify($password, $hash)
I believe the $password is the users password for login, now how/when/where do assign a value to $hash? since in my db i have email(username) password. Do i need to store the hash separately on the db? Can someone please enlighten me more
my login code
<?php
if(isset($_POST['login'])){
$password = $_POST['password'];
$stmt = $pdo->prepare("SELECT email, password FROM hash_test WHERE email=:email AND password=:password");
$stmt->execute(array(
':email' => $_POST['email'],
':password' =>$password
));
//if ($stmt->rowCount() ==1){
if (password_verify($password, $hash)) {
/* Valid */
echo "Right";
} else {
/* Invalid */
echo "wrong";
}
//}
}
?>
THANKS
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