Abstract: In this article, the author shows us various advanced OOP technologies in PHP through examples based on his understanding of OOP concepts. As the author said, "Imagination is the only limitation."
If you understand the basic OOP concepts, then I You will be shown more advanced techniques.
Serializing (Serializing)
PHP does not support persistent objects. In OOP, a persistent object is an object that can maintain state and functionality among references in multiple applications. This means having the ability to save the object to a file or database, and Load the object later. This is the so-called serialization mechanism. PHP has a serialization method that can be called on an object, and the serialization method can return a string representation of the object. However, serialization only saves the member data of the object and not the methods.
In PHP4, if you serialize the object into the string $s, then release the object, and then deserialize the object into $obj, you can continue to use the object's methods! I don't recommend doing this because (a) there is no guarantee in the documentation that this behavior will still work in future versions. (b) This may lead to a misunderstanding when you save a serialized version to disk and exit the script. When you run this script later, you can't expect that when you deserialize an object, the object's methods will be there, because the string representation doesn't include methods at all.
All in all, serialization in PHP is very useful for saving member variables of an object. (You can also serialize related arrays and arrays into a file).
Example:
<?php
$obj=new Classfoo();
$str=serialize($obj);
//Save $str to disk
//A few months later
//Load str from disk
$obj2=unserialize($str)
You restored the member data, but not the methods (according to the documentation). This results in the only way to access member variables (you have no other way!) by something like using $obj2->x, so don't try it at home.
There are some ways to solve this problem, I'm leaving them out because they are too bad for this succinct article. I would happily welcome fully serialized features in subsequent versions of PHP.
Using Classes for Data Storage One of the great things about PHP and OOP is that you can easily define a class to do something and call the corresponding class whenever you want to use it. Suppose you have an HTML form that allows the user to select a product by selecting the product ID number. There is product information in the database, and you want to display the product, its price, etc. You have different types of products, and the same action can mean different things to different products. For example, displaying a sound might mean playing it, but for other kinds of products it might mean displaying an image stored in a database. You can use OOP or PHP to reduce coding and improve quality.
Define a product class, define the methods it should have (for example: display), and then define a class for each type of product, derived from the product class (SoundItem class, ViewableItem class, etc.), covering the products Methods in classes to make them behave as you want.
Name the class according to the type field of each product in the database. A typical product table may have (id, type, price, description, etc. fields)... Then in the processing script, you can retrieve it from the database Get the type value from , and then instantiate an object named type:
<?php
$obj=new $type();
$obj->action();
This is a very good feature of PHP. You can call the display method or other methods of $obj without considering the type of the object. Using this technique, you don't need to modify the script to add a new type of object, just a class to handle it.
This function is very powerful. Just define methods without considering the types of all objects, implement them in different classes in different methods, and then use them in the main script for any object, no if...else, no Requires two programmers, only happy.
Now you agree that programming is easy, maintenance is cheap, and reusability is true?
If you manage a group of programmers, assigning work is simple; each person may be responsible for a type of object and the class that handles it.
Internationalization can be achieved through this technology, just apply the corresponding class according to the language field selected by the user, and so on.
Copying and Cloning
When you create an object of $obj, you can copy the object by $obj2=$obj. The new object is a copy (not a reference) of $obj, so it has the state of $obj at that time. Sometimes, you don't want to do this. You just want to generate a new object like the obj class. You can call the constructor of the class by using the new statement. This can also be achieved in PHP through serialization and a base class, but all other classes must be derived from the base class.
Entering the Danger Zone
When you serialize an object, you get a string in some format, which you can interrogate if you're interested, where, in the string, there is the name of the class (great!) and you can put It is taken out like:
＜?php
$herring=serialize($obj);
$vec=explode(':',$herring);
$nam=str_replace(""",'',$vec[2]) ;
So assuming you create a "Universe" class and force all classes to extend from universe, you can define a clone method in universe, as follows:
<?php
function clone() {
$herring=serialize($ this);
$vec=explode(':',$herring);
$nam=str_replace(""",'',$vec[2]);
$ret=new $nam;
return $ret;
}
}
/ /Then
$obj=new Something();
//Expand from Universe
$other=$obj->clone();
What you get is a new Something class object, which is the same as the object created by using the new method and calling the constructor. I don't know if this will work for you, but it's a good rule of thumb that the universe class knows the name of the derived class. Imagination is the only limit.
This statement writes the current time.