I'm new to oop and some lines of my code are only approximate, to indicate what I want to achieve.
I want to create a session with php within a function within a class and call it in another function.
class My_beautiful_class
{
public function index()
{
$_SESSION['ciao'] = 'ciao';
var_dump($_SESSION);
}
public function anotherfunction()
{
$this->index();
var_dump($_SESSION);
}
}
I just want to understand a concept: in this way, my code will work but, on the other end, it will execute everything it will find in my function index, in my other function anotherfunction. So, if I call two variable with the same name, I could have a problem.
I guess that in theory, I could handle the problem in another way which is that I could create a variable call sessionone for example and send it some values in with my index function:
class My_beautiful_class
{
public sessionone = [];
public function index()
{
$_SESSION['ciao'] = 'ciao';
$this->sessionone = $_SESSION['ciao'];
}
public function anotherfunction()
{
$this->sessionone;
var_dump($_SESSION);
}
}
, but I was wondering if there any way to for example call only one variable that lives in one function with my first approach.
Something like: (My code is wrong on purpose, it is only to indicate what I want to achieve)
public function index()
{
$_SESSION['ciao'] = 'ciao';
}
public function anotherfunction()
{
$this->index( $_SESSION['ciao'] );
}
}
The $_SESSION variable are what is called a Superglobal in PHP: http://php.net/manual/en/language.variables.superglobals.php This gives them a few unique traits.
First, Superglobals are accessible anywhere in your application regardless of scope. Setting the value of a superglobal key in one function will make the value accessible anywhere else in your application that you want to reference it.
Say for example we want to make a class to manage our session. That class may look something like this.
class SessionManager
{
public function __construct()
{
session_start(); //We must start the session before using it.
}
//This will set a value in the session.
public function setValue($key, $value)
{
$_SESSION[$key] = $value;
}
//This will return a value from the session
public function getValue($key)
{
return $_SESSION[$key];
}
public function printValue($key)
{
print($_SESSION[$key]);
}
}
Once we have a class to manage it a few things happen. We can use this new class to add info to the session and also to retrieve it.
Consider the following code:
$session = new SessionManager();
$session->setValue('Car', 'Honda');
echo $session->getValue('Car'); // This prints the word "Honda" to the screen.
echo $_SESSION['Car']; //This also prints the word "Honda" to the screen.
$session->printValue('Car'); //Again, "Honda" is printed to the screen.
Because of a session being a superglobal, once you set a value on the session it will be assessable anywhere in your application, either in or outside of the class itself.
You must call session_start() at the beginning of your class.
You can also start the session at the beginning of your code if you include your class like this sample
Remember that you can call the session_start only one time
Related
I need to access the global variable from another function. First I have assigned the value to global variable in one function. When I am trying to get that value from another function, it always returns null. Here my code is
StockList.php
<?php
$_current;
class StockList
{
public function report(){
global $_current;
$_current = 10;
}
public function getValue(){
print_r($GLOBALS['_current']);
}
}
?>
Suggestion.php
<?php
include ("StockList.php");
$stk = new StockList();
$stk->getValue();
?>
Thanks in advance.
Man, its hard to understand what are you trying to do as you said you have called report() in your index.php
Anyways, when dealing with classes, to set variable values, standard procedure is as following:
class StockList
{
public $_current;
public function setValue($value){
$this->current = $value;
}
public function getValue(){
return $this->current;
}
}
And after whenever you wanna use the class:
<?php
include ("StockList.php");
$stk = new StockList();
$stk->setValue(10);
$_current = $stk->getValue();
var_dump($_current);
?>
This is basic idea of OOP, benefits of this approach are:
You can dynamically set value of $_current.
Your getValue() function is not dedicated for printing the value of the variable, thats why you can use that function only for getting the value and then do whatever you want with it.
I need a variable which remains accessible across all the PHP files am using, i.e, I should be able to read it and change its value.
I tried to declare a class in a file with variable x:
In file1.php
public class sample{
public static $curruser = '0';
public function getValue() {
return self::$curruser;
}
public function setValue($val){
self::$curruser = $val;
}
}
Its being set in file2.php by calling sample::setValue($val). This page has a redirect to file3.php
I need to access this variable file3.php:
include 'file1.php';
print sample::getValue();
This gives me 0 instead of the value I set in file2.php.
Clearly, my understanding of static variables in PHP is a little shaky. Is there a proper way to do set and access the variable across files?
Try to use session or some sort of caching mechanism if you want data to persist between requests.
i recommend defining a constant like this:
define('CONSTANT_NAME' ,$value);
and access the value like this:
echo CONSTANT_NAME;
or using static function and static values and static functions like this:
public static function setValue($val){
self::$curruser = $val;
}
public static function getValue() {
return self::$curruser;
}
I'm writing now an app, which is supposed to be as simple as possible. My controllers implement the render($Layout) method which just does the following:
public function render($Layout) {
$this->Layout = $Layout;
include( ... .php)
}
I don't really understand the following problem: in my controller, I define a variable:
public function somethingAction() {
$someVariable = "something";
$this->render('someLayout');
}
in the php view file (same I have included in the render function) I try to echo the variable, but there is nothing. However, if I declare my action method like this:
public function somethingAction() {
global $someVariable;
$someVariable = "something";
$this->render('someLayout');
}
and in my view like this:
global $someVariable;
echo $someVariable;
it does work. Still it is annoying to write the word global each time.
How can I do this? I'd rather not use the $_GLOBAL arrays. In Cake PHP, for example, there is a method like $this->set('varName', $value). Then I can just access the variable in the view as $varName. How is it done?
From the PHP Manual on include:
When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward. However, all functions and classes defined in the included file have the global scope.
When you do
public function somethingAction() {
$someVariable = "something";
$this->render('someLayout');
}
the $someVariable variable is limited to the somethingAction() scope. Calling your render() method will not magically make the variable available in render(), because the render() method has it's own variable scope. A possible solution would be to do
public function somethingAction() {
$this->render(
'someLayout',
array(
'someVariable' => 'something'
)
);
}
and then change render() to
public function render($Layout, array $viewData) {
$this->Layout = $Layout;
include( ... .php)
}
You will then have access to $viewData in the included file, given that you are not trying to use it in some other function or method, e.g. if your included file looks like this:
<h1><?php echo $viewData['someVariable']; ?></h1>
it will work, but if it is looks like this:
function foo() {
return $viewData['someVariable'];
}
echo foo();
it will not work, because foo() has it's own variable scope.
However, a controller's sole responsibility is to handle input. Rendering is the responsibility of the View. Thus, your controller should not have a render() method at all. Consider moving the method to your View class and then do
public function somethingAction() {
$view = new View('someLayout');
$view->setData('someVariable', 'something');
$view->render();
}
The render() method of your View object could then be implemented like this:
class View
…
$private $viewData = array();
public function setData($key, $value)
{
$this->viewData[$key] = $data;
}
public function render()
{
extract($this->viewData, EXTR_SKIP);
include sprintf('/path/to/layouts/%s.php', $this->layout);
}
The extract function will import the values of an array in the current scope using their keys as the name. This will allow you to use data in the viewData as $someVariable instead of $this->viewData['someVariable']. Make sure you understand the security implications of extract before using it though.
Note that this is just one possible alternative to your current way of doing things. You could also move out the View completely from the controller.
Using global you're implicitly using the $_GLOBALS array.
A not recommended example, because globals are never a good thing:
function something() {
global $var;
$var = 'data';
}
// now these lines are the same result:
echo $_GLOBALS['var'];
global $var; echo $var;
Why don't you use simply the $this->set function?
public function render($Layout) {
$this->Layout = $Layout;
include( ... .php)
}
public function somethingAction() {
$this->set('someVariable', "something");
$this->render('someLayout');
}
// in a framework's managed view:
echo $someVariable;
I'm sorry not to know your framework in detail, but that makes perfectly sense.
Actually how it's done: There is a native extract function, that loads an associative array into the current symbol table:
array( 'var0' => 'val0', 'var1' => 'val1')
becomes
echo $var0; // val0
echo $var1; // val1
That's most likely 'what happens'.
I try to create some sort of setup class, like global values for the page.
The PHP-code
class globals
{
public $page;
public function __construct()
{
}
public function set_page($value)
{
$this->page = $value; // Maybe from a database
}
}
class get
{
public function page()
{
$globals = new globals();
return $globals->page;
}
}
$globals = new globals();
$globals->set_page('My value');
echo get::page(); // Short function to be in a template
Question
My class forget the value I set. Why is that?
Do I have to use global variables?
Is this the correct approach for the problem?
The variable is set on an object, not on a class.
For each class, you can instantiate multiple objects. Each of those have their own variable scope.
Edit:
I forgot to include the easiest, and least verbose solution to your problem. AFAIK, you're looking for a way to check what page you're on. Constants will do just that:
defined('MY_CURRENT_PAGE') || define('MY_CURRENT_PAGE','My Value');
//use anywhere like so:
echo 'Currently on page: '.MY_CURRENT_PAGE;
My class forget the value I set. Why is that?
Quite simple: your page member function isn't static, yet you call it as though it is: get::page(). Even if you were to fix this, you're creating a new instance in the page method, but you're not preserving a reference too it anywhere, so each page call will create a new globals instance, that has nothing set.
Do I have to use global variables?
No, unless you're Really desperate, never use globals
Is this the correct approach for the problem?
No, if it doesn't work, it's not correct (IMHO).
Well, what is, you might ask. There are several ways to go about this:
class globals
{
public static $page = null;//make this static, meaning all instances will share this var
public function set_page($value)
{
self::$page = $value; // Maybe from a database
}
}
class get
{
private $_globalsInstance = null;
public function __construct(globals $instance = null)
{
$this->_globalsInstance = $instance;
}
private function _getGlobals()
{
if (!$this->_globalsInstance instanceof globals)
{
$this->_globalsInstance = new globals();
}
return $this->_globalsInstance;
}
public function page()
{
return $this->_getGlobals()::$page;
}
}
Personally, however, I wouldn't work like this, I'd just pass my instances to wherever I need them (as arguments to functions/methods or just instantiate them in a scope that will be accessible:
class globals
{
public $page = null;//make this static, meaning all instances will share this var
public function set_page($value)
{
$this->page = $value; // Maybe from a database
}
}
$page = new globals();
$page->set_page('foobar');
someFunction($page);
$someObject->renderPage($page);
require_once('specificScript.php');
//inside required script:
echo $page->page;
Do I have to use global variables?
Not, if your can use PHP 5.3
Is this the correct approach for the problem?
Better to use a generic class for this, or use static properties of objects
<?php
class globals
{
public static $page;
public function __construct()
{
}
public function set_page($value)
{
self::$page = $value; // Maybe from a database
}
}
class get
{
public static function page()
{
return globals::$page;
}
}
$globals = new globals();
$globals->set_page('My value');
echo get::page(); // Short function to be in a template
P.S.
But this is not a nice approach
$globals there
class get
{
public function page()
{
$globals = new globals();
return $globals->page;
}
}
and there
$globals = new globals();
$globals->set_page('My value');
are different inctances of globals class.
One of the solutions is to make $page var static
public static $page;
I hope this helps
UPD:
Also you might apply Singleton to globals class and request for its insnance instead of creating new one directly:
globals::getInstance()->setPage('Page');
and
return globals::getInstance()->getPage();
In this case $page doesn't have to be static.
I'm not sure the other answers are very clear. You have created 2 classes. As such they have different scopes. As writen you can't access the original variable $page from the get class because it's outside the scope. Your page function in fact creates a new version of the object $globals without $page set. Normally you would place both your set and get functions in the initial object/class. Though it would be possible to use two class by calling the first class from the second and setting the page. Why you would want to do that I'm not sure.
if I were writing the class it would look like this.
class globals
{
public $page;
public function __construct()
{
}
public function set_page($value)
{
$this->page = $value; // Maybe from a database
}
public function get_page()
{
return $this->page;
}
}
Actually I would probably set page to private not public. As public I guess you don't need a get function.
for using methods of the class without object you must use static definition. but anyway you put value for one class object and try to get it from another...
Perhaps this will help you continue on your coarse:
class globals
{
public static $page;
public function set_page($value)
{
self::$page = $value; // Maybe from a database
}
}
class get extends globals
{
public function page()
{
$globals = new globals();
return parent::$page;
}
}
$globals = new globals();
$globals->set_page('My value');
echo get::page();
?>
I know you can assign a function's return value to a variable and use it, like this:
function standardModel()
{
return "Higgs Boson";
}
$nextBigThing = standardModel();
echo $nextBigThing;
So someone please tell me why the following doesn't work? Or is it just not implemented yet? Am I missing something?
class standardModel
{
private function nextBigThing()
{
return "Higgs Boson";
}
public $nextBigThing = $this->nextBigThing();
}
$standardModel = new standardModel;
echo $standardModel->nextBigThing; // get var, not the function directly
I know I could do this:
class standardModel
{
// Public instead of private
public function nextBigThing()
{
return "Higgs Boson";
}
}
$standardModel = new standardModel;
echo $standardModel->nextBigThing(); // Call to the function itself
But in my project's case, all of the information stored in the class are predefined public vars, except one of them, which needs to compute the value at runtime.
I want it consistent so I nor any other developer using this project has to remember that one value has to be function call rather then a var call.
But don't worry about my project, I'm mainly just wondering why the inconsistency within PHP's interpreter?
Obviously, the examples are made up to simplify things. Please don't question "why" I need to put said function in the class. I don't need a lesson on proper OOP and this is just a proof of concept. Thanks!
public $nextBigThing = $this->nextBigThing();
You can only initialize class members with constant values. I.e. you can't use functions or any sort of expression at this point. Furthermore, the class isn't even fully loaded at this point, so even if it was allowed you probably couldn't call its own functions on itself while it's still being constructed.
Do this:
class standardModel {
public $nextBigThing = null;
public function __construct() {
$this->nextBigThing = $this->nextBigThing();
}
private function nextBigThing() {
return "Higgs Boson";
}
}
You can't assign default values to properties like that unless that value is of a constant data type (such as string, int...etc). Anything that essentially processes code (such as a function, even $_SESSION values) can't be assigned as a default value to a property. What you can do though is assign the property whatever value you want inside of a constructor.
class test {
private $test_priv_prop;
public function __construct(){
$this->test_priv_prop = $this->test_method();
}
public function test_method(){
return "some value";
}
}
class standardModel
{
// Public instead of private
public function nextBigThing()
{
return "Higgs Boson";
}
}
$standardModel = new standardModel(); // corection
echo $standardModel->nextBigThing();