Call a function from a static property in PHP - php

I'm trying to directly call a function from a static property inside a class.
Here is an extract of my class:
class Uuid {
const VERSION_3 = 3;
const VERSION_5 = 5;
protected static $hash_function = [
self::VERSION_3 => 'md5',
self::VERSION_5 => 'sha1',
];
protected static function get_hash_value($value_to_hash, $version) {
// None of these work:
//$hash = self::$hash_function[$version]($value_to_hash);
//$hash = (self::$hash_function[$version])($value_to_hash);
//$hash = (self::$hash_function)[$version]($value_to_hash);
// Only this works:
$function = self::$hash_function[$version];
$hash = $function($value_to_hash);
return $hash;
}
}
The only way I've found of making it work so far is to store the function name in a temporary variable ($function) before calling it. I've tried wrapping the expression (or bits of the expression) in braces, ({,}), parentheses ((,)), prefixing a $, etc. but so far nothing has worked.
Is there a simple way of doing this without a temporary variable? If so, what is the minimum version of PHP this works for?

Yes, as you've discovered you need to store the function name as a complete string as a simple variable to be able to invoke it. The documentation for this functionality can be found at http://php.net/manual/en/functions.variable-functions.php
http://php.net/manual/en/function.call-user-func.php is another alternative.
call_user_func( static::$hash_function[$version], $value_to_hash );
See also is_callable(), call_user_func(), variable variables and function_exists().

Related

Passing optional configuration variables on class initialization in PHP

Bear with me please as I'm quite new to the OOP concept so I might just be way wrong in my thinking here.
I'm developing a class for some functionality I use quite often and I would like it to be configurable in any new project on initialization. The caveat here is that I'd like to set certain default variables and allow them to stay un-configured if the defaults are alright. Here is a bit of code to try to make the concept a bit clearer.
class someClass{
// Setting parameter defaults
private $param_a = 60;
private $param_b = 100;
/*
* The construct function. What I'd like to do here is make the param_a and param_b optional,
* i.e if it doesn't get set on initialization it takes the defaults from the class.
*/
function __construct($param_a, $param_b, $foo){
// do something ...
}
}
$foo = "some value";
// init example using defaults
$someclass = new someClass($foo); // $param_a and $param_b should be 60 and 100 respectively
// init example using custom options
$someclass = new someClass(40, 110, $foo);
Am I going in the right direction as far as how to set up class configuration? If so, how do I make param_a and param_b optional?
function __construct($foo, $param_a = 60, $param_b = 100){
// do something ...
}
You could supply required method arguments first, and then ones with default parameters afterwards, making them optional.
Then assign these to the class variables inside the constructor.
Another way would be to use func_get_args() and parse this.
You could just make the constructor take a general $args argument and merge it with an array of defaults:
public function __construct($args = array()) {
$args = array_merge(array(
'param_a' => 60,
'param_b' => 100,
'foo' => null
), $args);
foreach($args as $key => $val) {
$this->$key = $val;
}
}

When should one pass an object as a parameter vs instantiating?

I am curious about the best practices and any performance or other considerations relating to passing an instance of an object as a parameter to another function in the same class vs creating another instance of that object in the new function. Here's a quick example:
Option 1: Pass both instance of Trainee AND TraineeController to other functions
protected function startTraining($traineeID) {
$traineeController = new TraineeController();
$trainee = $traineeController->findTrainee($traineeID);
$this->initializeTraining($trainee, $traineeController);
$this->doSomeOtherStuffWithTrainee($trainee, $traineeController);
return Redirect::back()->with('trainee', $trainee);
}
protected function initializeTraining($trainee, $traineeController) {
$trainee->blah1 = 'red';
$trainee->blah2 = 'blue';
$propertiesToUpdate = [
'blah1' => $trainee->blah1,
'blah2' => $trainee->blah2
];
$traineeController->updateTrainee($trainee->traineeID, $propertiesToUpdate);
}
Option 2: Pass $trainee ONLY, instantiate a new TaineeController each time
protected function startTraining($traineeID) {
$traineeController = new TraineeController();
$trainee = $traineeController->findTrainee($traineeID);
$this->initializeTraining($trainee);
$this->doSomeOtherStuffWithTrainee($trainee);
return Redirect::back()->with('trainee', $trainee);
}
protected function initializeTraining($trainee) {
$trainee->blah1 = 'red';
$trainee->blah2 = 'blue';
$propertiesToUpdate = [
'blah1' => $trainee->blah1,
'blah2' => $trainee->blah2
];
$traineeController = new TraineeController();
$traineeController->updateTrainee($trainee->traineeID, $propertiesToUpdate);
}
In the above I need to pass $trainee across all functions each time instead of creating a new trainee from $traineeID because some other stuff goes on behind the scenes during the 'training' process that would otherwise be lost before relevant data is saved to the db. However, this is not required for TraineeController - I can either pass it as a parameter or instantiate a new TraineeController as much as I want. Which is the better choice?
I saw this question relating to C#, where the accepted answer was that passing an entire object is usually more efficient and instantiating another one because you are passing by reference. Does this hold true for PHP? Ie is the most efficient approach to pass the entire object by reference to required functions using &?
There is nothing wrong with passing an object as reference, but note that php expects that your function argument needs to expect a reference rather than just passing a variable by reference (php docs). php 5.4.0 will even raise a fatal error if this is not respected:
right:
protected function initializeTraining($trainee, &$traineeController) {}
$this->initializeTraining($trainee, $traineeController);
wrong:
protected function initializeTraining($trainee, $traineeController) {}
$this->initializeTraining($trainee, &$traineeController);
Passing objects by reference will in most cases have better performance than initiating the object again, but passing by reference could become tricky if your object has its own properties:
class TraineeController {
$fooCalled = false;
function foo(){ $this->fooCalled = true; }
function isFooCalled(){ return $this->fooCalled; }
}
$traineeController = new TraineeController();
$traineeController->foo();
//&$traineeController->isFooCalled() will be different from
//new TraineeController()->isFooCalled().

how to build a good router for php mvc

I'm experimenting with php mvc and I'm stucked with the following issue. My request and router classes are really simple and I would like to extend theme to can handle controller calls from sub folders and to controller classes functions should be able to pick up url variables send it threw get and post.
my router looks as it follows
class Router{
public static function route(Request $request){
$controller = $request->getController().'Controller';
$method = $request->getMethod();
$args = $request->getArgs();
$controllerFile = __SITE_PATH.'/controllers/'.$controller.'.php';
if(is_readable($controllerFile)){
require_once $controllerFile;
$controller = new $controller;
if(!empty($args)){
call_user_func_array(array($controller,$method),$args);
}else{
call_user_func(array($controller,$method));
}
return;
}
throw new Exception('404 - '.$request->getController().'--Controller not found');
}
}
and Request class
private $_controller;
private $_method;
private $_args;
public function __construct(){
$parts = explode('/',$_SERVER['REQUEST_URI']);
$this->_controller = ($c = array_shift($parts))? $c: 'index';
$this->_method = ($c = array_shift($parts))? $c: 'index';
$this->_args = (isset($parts[0])) ? $parts : array();
}
public function getController(){
return $this->_controller;
}
public function getMethod(){
return $this->_method;
}
public function getArgs(){
return $this->_args;
}
}
The problem is:when I try to send threw ajax, variables to a controller method this are not recognized because of its url structure.
For example
index/ajax?mod_title=shop+marks&domain=example
is accepted just if it look
index/ajax/shop+mark/example
Your code contains what is known as an LFI vulnerability and is dangerous in its current state.
You should whitelist your what can be used as your $controller, as otherwise an attacker could try to specify something using NUL bytes and possibly going up a directory to include files that SHOULD NOT be ever included, such as /etc/passwd, a config file, whatever.
Your router is not safe for use; beware!
edit: example on whitelisting
$safe = array(
'ajax',
'somecontroller',
'foo',
'bar',
);
if(!in_array($this->_controller, $safe))
{
throw new Exception(); // replace me with your own error 404 stuff
}
Since your Request class uses a URI segments approach for identifying controller, action and arguments, global variables such as $_GET or $_REQUEST are not taken into account from within your Request.
What you need to do is to make some additions to your Request code. Specifically:
Remove the line:
$this->_args = (isset($parts[0])) ? $parts : array();
And add the following:
$all_parts = (isset($parts[0])) ? $parts : array();
$all_parts['get'] = $_GET;
$this->_args = $all_parts;
This way, $_GET (ie variables passed via the url) variables will be available in the actions called, as they will be in $args (they will be available as $args['get'] actually, which is the array that holds the $_GET vars, so you will be able to have access to domain=example by using $args['get']['domain']).
Ofcourse, you can add one more method in your Request class (e.g. query) that might look like that:
public function query($var = null)
{
if ($var === null)
{
return $_GET;
}
if ( ! isset($_GET[$var]) )
{
return FALSE;
}
return $_GET[$var];
}
This way, you can get a single variable from the url (e.g. $request->query('domain')) or the whole $_GET array ($request->query()).
That's because php will put "?mod_title=..." in the $_GET array automatically. Your getArgs() function should check for $_GET, $_POST or $_REQUEST.
If you're trying for a minimal MVC approach, have a look at rasmus' example: http://toys.lerdorf.com/archives/38-The-no-framework-PHP-MVC-framework.html
If your use case is going to get more complex, have a look at how Zend (http://framework.zend.com/manual/en/zend.controller.html) or Symfony (https://github.com/symfony/symfony/tree/master/src/Symfony/Component/Routing) do their stuff.
Choose any popular MVC to see how they implement it under the hood. In addition, spl_autoload_register and namespace are your friends.

Is there any way to reset all static properties of a particular class?

Static properties make testing hard as you probably know. Is there no way to reset all static properties of a particular class back to their initial state? Ideally this would not require custom code for each class, but could be used in a general way by inheritance, or from outside of the class completely.
Please do not reply with something like, "don't use static properties". Thanks.
Assuming you're using PHPUnit:
See the PHPUnit Manual section about global state. Static members are covered by this if you have PHP 5.3 or higher. Static members are not part of serialization (in case you wonder).
See as well #backupGlobals and #backupStaticAttributes
No. PHP does not preserve that information.
I was toying around with ReflectionClass and ::getDefaultProperties and ::getStaticProperties, but they only return the current state.
You will have to create an array with the default values, then manually foreach over them and reset your class attributes.
I couldn't find any way to include or require classes or functions many times without getting an error.
Anyway, if you need to replace functions inside an structure you should make an array/ArrayObject of lamdas/inline functions (like javascript objects)
When you re import the array it will back to the original state.
$Animal = array(
'eat' => function($food) {/*...*/},
'run' => function($to_place) {/*...*/}
);
$Animal['eat'] = function($food) {/* new way to eat */}
I also managed to reset the state of static attributes by using Reflections. For this approach you need to use a convention attribute naming for default value of each type.
class MyStaticHolder {
public static $x_array = array();
public static $x_num = 0;
public static $x_str = '';
}
//change values
MyStaticHolder::$x_array = array(1,2,4);
MyStaticHolder::$x_num = -1.4;
MyStaticHolder::$x_str = 'sample-text';
function reset_static($class_name) {
$z = new ReflectionClass($class_name);
$properties = $z->getDefaultProperties();
print_r($properties);
foreach ($properties as $property_name => $value) {
$sufix = end(explode('_',$property_name));
switch ($sufix) {
case 'array':
$class_name::$$property_name = array();
break;
case 'num':
$class_name::$$property_name = 0;
break;
case 'str':
$class_name::$$property_name = '';
break;
default:
$class_name::$$property_name = null;
break;
}
}
}
reset_static('MyStaticHolder');

Issue with assigning class variable in PHP

I am trying to assign a variable to a class in PHP, however I am not getting any results?
Can anyone offer any assistance? The code is provided below. I am trying to echo the URL as shown below, by first assigning it to a class variable.
class PageClass {
var $absolute_path = NULL;
function get_absolute_path(){
$url = $this->absolute_path;
echo $url;
}
}
$page = new PageClass();
$page->absolute_path = "http://localhost:8888/smile2/organic/";
$page->get_absolute_path(); //this should echo the URL as defined above - but does not
It also works for me.
Take a look at a live example of your code here.
However, there are a few things you should change about your class.
First, Garvey does make a good point that you should not be using var. That's the older PHP4, less OOP conscious version. Rather declare each variable public or private. In fact, you should declare each function public or private too.
Generally, most classes have private variables, since you usually only want to change the variables in specific ways. To achieve this control you usually set several public methods to allow client functions to interact with your class only in restricted predetermined ways.
If you have a getter, you'd probably want a setter, since these are usually used with private variables, like I described above.
A final note is that functions named get usually return a value. If you want to display a value, it is customary to use a name like display_path or show_path:
<?php
class PageClass
{
private $absolute_path = NULL;
public function set_absolute_path($path)
{
$this->absolute_path = $path;
}
public function display_absolute_path()
{
echo $this->absolute_path;
}
}
$page = new PageClass();
$page->set_absolute_path("http://localhost:8888/smile2/organic/");
$page->display_absolute_path();
// The above outputs: http://localhost:8888/smile2/organic/
// Your variable is now safe from meddling.
// This:
// echo $this->absolute_path;
// Will not work. It will create an error like:
// Fatal error: Cannot access private property PageClass::$absolute_path on ...
?>
Live Example Here
There's a section on classes and objects in the online PHP reference.
class PageClass {
public $absolute_path = NULL;
function get_absolute_path(){
$url = $this->absolute_path;
return $url;
}
}
$page = new PageClass();
$page->absolute_path = "http://localhost:8888/smile2/organic/";
echo $page->get_absolute_path();
Works fine for me.
Have you checked that the script and esp. the code in question is executed at all?
E.g. add some unconditional debug-output to the script. Or install a debugger like XDebug to step through the code and inspect variables.
<?php
class PageClass {
var $absolute_path = NULL; // old php4 declaration, see http://docs.php.net/oop5
function get_absolute_path() { // again old php4 declaration
$url = $this->absolute_path;
echo "debug: "; var_dump($url);
echo $url;
}
}
$page = new PageClass();
$page->absolute_path = "http://localhost:8888/smile2/organic/";
echo "debug: page->get_absolute_path\n";
$page->get_absolute_path();

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