Difference between PHP4 and PHP5

[Balamohan]

I have worked with PHP4 for quite a time and I have a good knowledge about the language. Now, I want to use PHP5. But, I want to know that if there is a great difference between PHP4 and PHP5. Will it be simple or confusing for the programmers who have already used PHP4? What are the additional features of PHP5 as compared to PHP4? People with knowledge about PHP are requested to reply with suitable solutions.

[Katty]

Taking about the difference between PHP4 and PHP5, it is the OOP feature that has a significant change. In, PHP4 everything including the objects were passed by value. In PHP5, this has been changed and everything including the objects are passed by reference. So, this has greatly helped the programmers using PHP4. If you have a good knowledge of PHP4, you will not find any great difference among the the two languages.

[Reegan]

The problem that the programmers had in PHP4 was that inorder to create a duplicate of an object, it was simply copied and assigned to another variable. This has completely changed in PHP5. Here, you will get the "clone" keyword, that is a new addition to this version. This is a major difference between PHP4 and PHP5, that is worth mentioning, otherwise most of the things are same.

[Modifier]

The major difference between PHP4 and PHP5 is that PHP5 allows to create class constants that act in the same way we do for the defined constants. The only thing to be kept in mind is that it must be contained inside a class definition. The :: operator can be used to access it. With this feature coming into PHP5, you will no longer be required to use the & operator, that is also called as the reference operator.

[MindSpace]

You will be able to use the static methods and properties in PHP5. This is the major difference between PHP4 and PHP5. Whenever a class is defined as static, it is able to access the members with the help of the :: operator without having to use an instance. This has greatly helped the programmers to reduce the time that they used for creating the instance of the classes, that is the objects.

[opaper]

According to me the greatest difference between PHP4 and PHP5 is that there is visibility for the class methods and the properties. The 3 visibilities available are:

1. PUBLIC
2. PROTECTED
3. PRIVATE

It has also introduced an entirely new names for the constructors and destructors that are unified. It also allows you to define an abstract class. The best feature is that I liked is the introduction of interfaces and also the magic methods that makes it totally different from the previous version.