So for example I have this code:
class Object{
public $tedi;
public $bear;
...some other code ...
}
Now as you can see there are public variables inside this class. What I would like to do is to make these variables in a dynamic way, with a function something like:
private function create_object_vars(){
// The Array what contains the variables
$vars = array("tedi", "bear");
foreach($vars as $var){
// Push the variables to the Object as Public
public $this->$var;
}
}
So how should I create public variables in a dynamic way?
$vars = (object)array("tedi"=>"bear");
or
$vars = new StdClass();
$vars->tedi = "bear";
Yes, you can do this.
You're pretty much correct - this should do it:
private function create_object_vars(){
// The Array of names of variables we want to create
$vars = array("tedi", "bear");
foreach($vars as $var){
// Push the variables to the Object as Public
$this->$var = "value to store";
}
}
Note that this makes use of variable variable naming, which can do some crazy and dangerous things!
As per the comments, members created like this will be public - I'm sure there's a way of creating protected/private variables, but it's probably not simple (eg you could do it via the C Zend API in an extension).
As alternative, you can also derive your object from ArrayObject. So it inherits array-behaviour and a few methods which make injecting attributes easier.
class YourObject extends ArrayObject {
function __construct() {
parent::__construct(array(), ArrayObject::PROPS_AS_ARRAY);
}
function create_object_vars() {
foreach ($vars as $var) {
$this[$var] = "some value";
}
}
Attributes will then be available as $this->var and $this["var"] likewise, which may or not may suit the use case. The alternative method for setting attributes would be $this->offsetSet("VAR", "some value");.
Btw, there is nothing evil about variable variables. They're a proper language construct, as would be reusing ArrayObject.
Related
I'd like to do something like this:
public static function createDynamic(){
$mydynamicvar = 'module';
self::$mydynamicvar = $value;
}
and be able to access the property from within the class with
$value = self::$module;
I don't know exactly why you would want to do this, but this works. You have to access the dynamic 'variables' like a function because there is no __getStatic() magic method in PHP yet.
class myclass{
static $myvariablearray = array();
public static function createDynamic($variable, $value){
self::$myvariablearray[$variable] = $value;
}
public static function __callstatic($name, $arguments){
return self::$myvariablearray[$name];
}
}
myclass::createDynamic('module', 'test');
echo myclass::module();
static variables must be part of the class definition, so you can't create them dynamically. Not even with Reflection:
chuck at manchuck dot com 2 years ago
It is important to note that calling ReflectionClass::setStaticPropertyValue will not allow you to add new static properties to a class.
But this looks very much like a XY Problem. You probably don't really want to add static properties to a PHP class at runtime; you have some use case that could be fulfilled also that way. Or that way would be the fastest way, were it available, to fulfill some use case. There well might be other ways.
Actually the use cases below are yet again possible solutions to some higher level problem. It might be worth it to reexamine the high level problem and refactor/rethink it in different terms, maybe skipping the need of meddling with static properties altogether.
I want a dictionary of properties inside my class.
trait HasDictionary {
private static $keyValueDictionary = [ ];
public static function propget($name) {
if (!array_key_exists($name, static::$keyValueDictionary) {
return null;
}
return static::$keyValueDictionary[$name];
}
public static function propset($name, $value) {
if (array_key_exists($name, static::$keyValueDictionary) {
$prev = static::$keyValueDictionary[$name];
} else {
$prev = null;
}
static::$keyValueDictionary[$name] = $value;
return $prev;
}
}
class MyClass
{
use Traits\HasDictionary;
...$a = self::propget('something');
self::propset('something', 'some value');
}
I want to associate some values to a class, or: I want a dictionary of properties inside some one else's class.
This actually happened to me and I found this question while investigating ways of doing it. I needed to see, in point B of my workflow, in which point ("A") a given class had been defined, and by what other part of code. In the end I stored that information into an array fed by my autoloader, and ended up being able to also store the debug_backtrace() at the moment of class first loading.
// Solution: store values somewhere else that you control.
class ClassPropertySingletonMap {
use Traits\HasDictionary; // same as before
public static function setClassProp($className, $prop, $value) {
return self::propset("{$className}::{$prop}", $value);
}
public static function getClassProp($className, $prop) {
return self::propget("{$className}::{$prop}");
}
}
// Instead of
// $a = SomeClass::$someName;
// SomeClass::$someName = $b;
// we'll use
// $a = ClassPropertySingletonMap::getClassProp('SomeClass','someName');
// ClassPropertySingletonMap::setClassProp('SomeClass','someName', $b);
I want to change, not create, an existing property of a class.
// Use Reflection. The property is assumed private, for were it public
// you could do it as Class::$property = $whatever;
function setPrivateStaticProperty($class, $property, $value) {
$reflector = new \ReflectionClass($class);
$reflector->getProperty($property)->setAccessible(true);
$reflector->setStaticPropertyValue($property, $value);
$reflector->getProperty($property)->setAccessible(false);
}
Static properties must be defined in the class definition. Therefore, real static properties cannot be created dynamically like regular properties.
For example, if you run this:
<?php
class MyClass
{
public static function createDynamic()
{
$mydynamicvar = 'module';
self::$mydynamicvar = $value;
}
}
MyClass::createDynamic();
var_dump(MyClass::$mydynamicvar);
var_dump(MyClass::$module);
...you'll get this error
Fatal error: Access to undeclared static property: MyClass::$mydynamicvar test.php on line 8
Notice how the error occurs on line 8 when trying to set the property instead of line 14 or 15 (as you might expect if you were simply doing it wrong and dynamically creating static properties was actually possible).
A related problem that IS possible (in PHP 5.4.0 and up) is to include various separate groups of static variable or constant declarations and group them together into one class declaration.
Here is an example:
trait Added1 // This can be located in one Include file
{
static
$x="hello"; // Can declare more variables here
}
trait Added2 // This can be located in another Include file
{
static
$y="world"; // Can declare more variables here
}
class G // Global constant and variable declarations class
{
use Added1, Added2; // Combines all variable declarations
}
echo G::$x." ".G::$y; // Shows "hello world" on the web page
Is it possible to run a function when referring to a variable in a php class rather than simply returning its value, similar to javascript's ability for a variable to hold a method?
class LazyClassTest()
{
protected $_lazyInitializedVar;
public function __construct()
{
/* // How can this call and return runWhenReferrenced() when
// someone refers to it outside of the class:
$class = new LazyClass();
$class->lazy;
// Such that $class->lazy calls $this->runWhenReferrenced each
// time it is referred to via $class->lazy?
*/
$this->lazy = $this->runWhenReferrenced();
}
protected function runWhenReferrenced()
{
if (!$this->_lazyInitializedVar) {
$this->_lazyInitializedVar = 'someValue';
}
return $this->_lazyInitializedVar
}
}
PHP5s magic method __get($key) and __set($key, $value) might be what you need. More information about them is available in the PHP manual.
This sounds like PHP5.3: lambda / closures / anonymous functions
http://php.net/manual/en/functions.anonymous.php:
<?php
$greet = function($name) {
printf("Hello %s\r\n", $name);
};
$greet('World');
$greet('PHP');
?>
You are probably heading in the wrong direction. You normally want to define a getter getLazyVar(). There is a reason why people always make properties protected and defined getters / setters: So they can pre- or postprocess the values.
Assuming I have a Config class that I use to access the config vars from everywhere (Config::X).
Is it possible to implement a function that can be called from outside the class that adds and/or modifies properties?
Something like this is what I'm thinking of:
class Config
{
const myVar = 'blah';
public static function write( $name, $value )
{
//....
}
}
echo Config::myVar; // Clear
Config::write( 'test', 'foo' );
echo Config::test; // Should be foo
I've seen something similiar in CakePHP but couldn't figure out the solution.
My goal would be being able to write to the base Config class from different files, e.g.: store Database information in a separate file.
You can't achieve this without declaring the variables first unless you ditch static variables and use concrete implementations instead. Even if you do declare the variables first you will have to call them using `$:
class Config {
const $myVar = 'blah';
public static $test;
public static function write( $name, $value )
{
//....
}
}
Config::write( 'test', 'foo' );
echo Config::$test; // Will be foo
If you have a concrete implementation then you can leverage __get and __set so you don't have to declare all your variables.
class Config {
const $myVar = 'blah';
private $vars = array();
public function __set($name, $value) {
$this->vars[$name] = $value;
}
public function __get($name) {
if(isset($this->vars[$name])
return $this->vars[$name];
return null;
}
}
echo Config::myVar; // Still the same
$config = new Config();
$config->test = 'foo';
echo $config->test; // Will be foo
This will mean you'll need to pass around your config object if you need it somewhere. If you find this annoying you might want to look into dependency injection.
You can't modify values of a static class. If you would like to have this functionality, you'll need to make an instance of the class,and store in it session if you need the values to persist over pages.
Your code seems to make the write function bind up a new const called $name .... never seen that done before.
I'm not sure if this is a trivial questions but in a PHP class:
MyClass:
class MyClass {
public $var1;
public $var2;
constructor() { ... }
public method1 () {
// Dynamically create an instance variable
$this->var3 = "test"; // Public....?
}
}
Main:
$test = new MyClass();
$test->method1();
echo $test->var3; // Would return "test"
Does this work?? How would I get this to work? Ps. I wrote this quickly so please disregard any errors I made with setting up the class or calling methods!
EDIT
What about making these instance variables that I create private??
EDIT 2
Thanks all for responding - Everyone is right - I should have just tested it out myself, but I had an exam the next morning and had this thought while studying that I wanted to check to see if it worked. People keep suggesting that its bad OOP - maybe but it does allow for some elegant code. Let me explain it a bit and see if you still think so. Here's what I came up with:
//PHP User Model:
class User {
constructor() { ... }
public static find($uid) {
$db->connect(); // Connect to the database
$sql = "SELECT STATEMENT ...WHERE id=$uid LIMIT 1;";
$result = $db->query($sql); // Returns an associative array
$user = new User();
foreach ($result as $key=>$value)
$user->$$key = $value; //Creates a public variable of the key and sets it to value
$db->disconnect();
}
}
//PHP Controller:
function findUser($id) {
$User = User::find($id);
echo $User->name;
echo $User->phone;
//etc...
}
I could have just put it in an associative array but I can never correctly name that array something meaningful (ie. $user->data['name'] ... ugly.) Either way you have to know what is in the database so I do not really understand what the argument is that its confusing, especially since you can just var dump objects for debugging.
Why dont you just write the code and see for yourself?
<?php
class Foo
{
public function __construct()
{
$this->bar = 'baz';
}
}
$foo = new Foo;
echo $foo->bar; // outputs 'baz'
and
var_dump($foo);
gives
object(Foo)#1 (1) {
["bar"] => string(3) "baz"
}
but
$r = new ReflectionObject($foo);
$p = $r->getProperty('bar');
var_dump($p->isPublic());
will throw an Exception about 'bar' being unknown, while
$r = new ReflectionObject($foo);
$p = $r->getProperties();
var_dump($p[0]->isPublic());
will return true.
Now, should you do this type of assignment? Answer is no. This is not good OOP design. Remember, OOP is about encapsulation. So, if bar is describing some public property of the class, make it explicit and declare it in your class as public $bar. If it is supposed to be private declare it as private $bar. Better yet, dont use public properties at all and make them protected and provide access to them only through getters and setters. That will make the interface much more clearer and cleaner as it conveys what interaction is supposed to be possible with an object instance.
Assigning properties on the fly here and there across your code, will make maintaining your code a nightmare. Just imagine somewhere along the lifecylce of Foo someone does this:
$foo = new Foo;
$foo->monkey = 'ugh';
echo $foo->monkey; // outputs 'ugh'
Now, from looking at the class definition above, there is absolutely no way, a developer can see there is now a monkey patched into Foo. This will make debugging a pain, especially if code like this is frequent and distributed across multiple files.
Yes that will indeed work. Auto-created instance variables are given public visibility.
yes that works as you'd hope/expect.
I you wanted to make private variables on the fly you could use php magic functions to emulate this, e.g
MyClass
<?php
class MyClass {
public $var1;
public $var2;
private $data = array();
public function __get($key) {
// for clarity you could throw an exception if isset($this->data[$key])
// returns false as it is entirely possible for null to be a valid return value
return isset($this->data[$key]) ? return $this->data[$key] : null;
}
public function __set($key, $value) {
$this->data[$key] = $value;
}
}
?>
Main
<?php
$test = new MyClass();
$test->myVar = 'myVar is technically private, i suppose';
echo $this->myVar; // 'myVar is technically private
?>
Although these dynamically created variables are technically private, they are infact publicly accessible... i cannot image the purpose for wanting to dynamically create private instance variables. I would question your design.
Did you try it?
It is possible but you might get strict errors. If you dynamically need to create these variables, you are probably doing something wrong.
You should either change this into a function:
function var($no) { .. }
or use __get (http://ca.php.net/manual/en/language.oop5.overloading.php#language.oop5.overloading.members)
In PHP, how do you use an external $var for use within a function in a class? For example, say $some_external_var sets to true and you have something like
class myclass {
bla ....
bla ....
function myfunction() {
if (isset($some_external_var)) do something ...
}
}
$some_external_var =true;
$obj = new myclass();
$obj->myfunction();
Thanks
You'll need to use the global keyword inside your function, to make your external variable visible to that function.
For instance :
$my_var_2 = 'glop';
function test_2()
{
global $my_var_2;
var_dump($my_var_2); // string 'glop' (length=4)
}
test_2();
You could also use the $GLOBALS array, which is always visible, even inside functions.
But it is generally not considered a good practice to use global variables: your classes should not depend on some kind of external stuff that might or might not be there !
A better way would be to pass the variables you need as parameters, either to the methods themselves, or to the constructor of the class...
Global $some_external_var;
function myfunction() {
Global $some_external_var;
if (!empty($some_external_var)) do something ...
}
}
But because Global automatically sets it, check if it isn't empty.
that's bad software design. In order for a class to function, it needs to be provided with data. So, pass that external var into your class, otherwise you're creating unnecessary dependencies.
Why don't you just pass this variable during __construct() and make what the object does during construction conditional on the truth value of that variable?
Use Setters and Getters or maybe a centralized config like:
function config()
{
static $data;
if(!isset($data))
{
$data = new stdClass();
}
return $data;
}
class myClass
{
public function myFunction()
{
echo "config()->myConfigVar: " . config()->myConfigVar;
}
}
and the use it:
config()->myConfigVar = "Hello world";
$myClass = new myClass();
$myClass->myFunction();
http://www.evanbot.com/article/universally-accessible-data-php/24