Skip to main content

Methods overloading in PHP

Yesterday, one of my friend, coworker wanted to know about how to overload methods in PHP. So, I decided to write something about this in my blog, because there may be many programmers who faced this problem.

Method overloading is common in many object-oriented languages but is not as use-ful in PHP because you tend to use flexible types and the (easy-to-implement) optional function parameters instead. Therefore the method overloading in PHP is implemented some what differently than other programing languages such as Java.

In PHP there is a special class method for implemenging methods overloading. In PHP there are a number of class methods with special meanings whose names begin with a double underscore (__), such as __get(), __set(), __construct(), and __destruct(). Here, we use the method __call(), which is used in PHP to implement method overloading.

To use it, you implement a __call() method, as given below:
public function __call($method, $param){

if ($method == ‘display’) {
if (is_object($param[0]))
$this->displayObject($param[0]);
else if (is_array($param[0]))
$this->displayArray($param[0]);
else
$this->displayScalar($param[0]) ;
}
}

The __call() method should take two parameters.The first contains the name of the method being invoked, and the second contains an array of the parameters passed to that method.You can then decide for yourself which underlying method to call. In this case, if an object is passed to method display(), you call the underlying displayObject() method; if an array is passed, you call displayArray(); and if something else is passed, you call displayScalar().

To invoke this code, you would first instantiate the class containing this __call() method (name it overload) and then invoke the display() method, as in this example:
$ov = new overload;
$ov->display(array(1, 2, 3));
$ov->display(‘cat’);

The first call to display() invokes displayArray(), and the second invokes displayScalar().

Referenceses:

  • PHP and MySQL Web Development, Luke Welling and Laura Thomson, Third Edition.

  • Official PHP documentation – http://php.net

Comments

  1. "Method overloading is common in many object-oriented languages but is not as use-ful in PHP because you tend to use flexible types and the (easy-to-implement) optional function parameters instead. Therefore the method overloading in PHP is implemented some what differently than other programing languages such as Java. "
    Thanks for the information

    ReplyDelete
  2. This is completely unsatisfactory. for example you can't tell a development environment about the methods that __call will implement and you have to hand craft your own __call for every class where you want to override methods.

    This is the single most important thing holding PHP back as a proper OO language and it is more than about time it was addressed.

    Kind regards
    Greg

    ReplyDelete
  3. Yes, you have to write some additional codes to overload the methods in php. This is because of the PHP's flexible data types.

    In PHP there are no restrictions for bad practices, it is a self disciplinary practice of developers to follow good practices. Therefore, PHP can be used for both small scale and enterprise level projects.

    Actually, according to my point of view, there no bad languages, but some bad developers are there.

    Thanks for the comment...

    Regards

    ReplyDelete

Post a Comment

Popular posts from this blog

How to create a new module for vtiger...

Recently, I had to create a new module for vtigerCRM for my client in current working place. I did search in many places including the official vtiger sites, but couldn’t find a better documentation for my purpose. The latest vtiger version at that time was 5.0.3. Because I had some experience doing lots of core modifications for this system, I did decide to read the source code and find how to add a new module. Finally, I could create a new module and started the project. So, I thought it will be a good thing to write some thing on my blog about this topic, so that others who want to do this thing can read. Given below is a brief description about how to create a new module for vtiger CRM 5.0.3. Source code of this example module is also available to Download.
Step 01: Creating the module directory and minimum required files.
Create a directory called “newModule” inside your vtiger modules directory, or any other name that you prefer. Now, module index file should be created. Create a…

De Morgan's Laws in Programming

Recently, while I was reviewing some codes, I saw there were some conditional statements that check for the same condition but written in different ways. Most of these statements were written with common sense without using any mathematical analysis, since those are too simple to go for a more formal approach. The two identical conditional statements that has been written in different ways are given below.

01)

if ($comment['deleted'] == '1' || $comment['approved'] == '0') {
                unset($conversationsArray[$key]);
} else {
               ++$count;
}

02)

if ($comment['deleted'] == '0' && $comment['approved'] == '1') {
               ++$count;             
} else {
             unset($conversationsArray[$key]);
}

Obviously, the above lines say that the inverse of the first condition is equals to the second condition and vice versa. That is...

 ($comment['deleted'] == '1' || $comment['ap…

How to create a simple Web Crawler

Web crawlers are used to extract information from web sites for many purposes.

The simple example given here accepts an URL and exposes some functions to query the content of the page.

To check out the source code of this example : https://github.com/nadeeth/crawler

If you are going to make any improvements to this code, I recommend you to follow TDD and use the unit test class in the code.

Step 1 : Create the class, init function and required attributes In this example, xpath is used for querying the given web page. There is an attribute to hold the page url, and another to hold the xpath object of the loaded page.

The init() function initializes the xpath object for the page URL assigned to url attribute.

class Crawler { public $url = false; protected $xpath = false; public function init() { $xmlDoc = new DOMDocument(); @$xmlDoc->loadHTML(file_get_contents($this->url)); $this->xpath = new DOMXPath(@$xmlDoc); } } In the next two ste…