In Object Oriented Programming, inheritance is a commonly used mechanism to model the relationship between two types. However, modelling such relationship without realizing the impact on the overall application may result in unexpected problems. In this article, I will try to present some internal details of inheritance mechanism based on the Java language and highlight some of the problems that a developers should be aware of when using inheritance of types.

Virtual Private Network (VPN) is a method for connecting between network nodes by utilizing Internet connection (Public Network / WAN) and using encrypted protocol so it is more secure. VPN is one of the best solutions to connect multiple remote locations to easily take advantage of each location’s Internet connection.

An example of this is when you manage a network for multiple offices in different locations and away from each other. To connect the office ‘A’ using a physical link will certainly require a large cost. Well, by using VPN we can build an inter-office link by utilizing the existing internet network. Links that are formed complete with encryption so as to minimize the possibility of data will be accessed by people who are not responsible.

Regular Expression Functions

ereg_replace() and eregi_replace()
The ereg_replace() and eregi_replace() functions replace instances of a pattern within a string and return the new string. The ereg_replace() function performs a clase-sensitive match, and eregi_replace() performs a case-insensitive match. Here is the syntax for both functions:

ereg_replace(pattern, replacement, string);
eregi_replace(pattern, replacement, string);

For example, you would use the following code to replace “ASP” with “PHP” in the string “I really love programming in ASP”:

Databases

Why not store parameters in a database? If your application is already using a database, you might consider defining a special table for this purpose. To hold key-value pairs you need two columns of type char: “key” and “value”. If you want a really flexible solution you should consider making a small (Swing or web?) application that can be used to insert and update the data in this table.

Program Execution Functions
You can use PHP’s built in program execution functions to use programs residing on your system, such as encryption programs, third-party image manipulation programs, and so forth. For all program execution functions, the PHP user much have permission to execute the given program.

exec()
The exec() function executes an external program. its syntax is

exec(command, [array], [return_var]);

If an array is specified, the output of the exec() function will append to the array. If return_var is specified, it will be assigned a value of the program’s return status.