Welcome to ProfWebDev.com WEB log

Welcome to ProfWebDev WEB log. The blog is devoted to WEB development, WEB Security, and SEO optimization. We are going to talk about PHP and ASP.NET development. They are the most attractive WEB development languages for me. The other languages are powerful too, bit I like these ones. PHP and ASP.NET allow me to create sites any kind of difficulty.

Sometimes I use PHP but sometimes I use ASP.NET. Why I choose one of the languages? I don’t know. I just choose one. It depends on my mood. Sometimes it depends of weather.

Introduction to PHP

PHP commands are inserted right into HTML documents. But how does the web server can tell the PHP code to be executed embedded into the HTML document? Actually, it’s very easy: Special tags are used to indicate the beginning and the end of the PHP code. Everything outside of these tags is treated as HTML code.

Most often, the beginning and the end of PHP commands are marked in the following way:

<?php
 PHP code
?>

Everything between the tags the web server treats as PHP code and processes it accordingly. Everything outside of these tags is treated as HTML code and is sent to the client as is and is processed in the browser.

This is the most preferential format of the PHP code delimiting tags; using it you can be certain that it will processed by the server correctly. There also are other currently supported PHP code delimiting formats. Despite this, you should realize that only the tags are guaranteed support in all PHP versions. Use of other PHP code delimiting tags may be discontinued or limited in any future version of the language. This may lead to the problem of having to rewrite all the scripts in which discontinued delimiters are used. It’s no big deal if you have only a few of them, but if you have a big site with lots of PHP scripts, then you’ve got a problem.

Including files

Every programmer tries to reuse existing code and any programming language tries to provide support for this. When we develop a new project, we don't feel at all as solving the same problems that had been solved in previous projects. Being able to reuse already developed code allows us to avoid doing the same mundane routines over and over again.

You have probably heard a lot about Windows dynamic libraries. These libraries store various different resources (images, icons, dialog window forms, menus, etc.) and/or program code. Any program can load this library and use the resources stored in it. For example, the OpenGL graphics library stores functions for creating 3D graphics of practically any complexity. Any programmer can load this library into the computer memory and use its resources in his or her own projects. Accordingly, it is not necessary to write graphic functions code for each new program, but use code already developed by other programmers.

Dynamic libraries not only allow a programmer use his or her own code in different projects, but also share it with other programmers, as we saw in the example with the OpenGL library.

Being able to reuse code is even more important when programming web pages. Your site may contain hundreds of files doing the same thing. Writing the same piece of code in each of them is a tedious time-consuming task. Moreover, this results in bloated, slow-executing files.

Outputing information on the page

We already used the print function to observe the results of script execution. We have to explore the available output functions more closely, because if you can`t see the results of your scripts` work, you may have problems digesting the material presented. The best way to learn anything is to personally touch and see every detail.

In addition to the print function, information can be displayed by the echo function. There are two ways of calling it. These are the following:

echo("Hello, this is text");
echo "Hello, this is text";

In the first case, the text to be displayed in placed into parenthesis, and in the other, it is simply placed after the function name after a space. In either case, the output text is enclosed into quotation marks. Both calling method are equivalent to each other, and you can use the one you feel more comfortable with. You can output several strings with the echo function by separating them with a comma. For example:

Comments in PHP

The format of PHP comments is similar to that of C/C++ and Java, which is another indication of these languages being related. What is a comment as related to a programming language? This is supplementary information given in the code that has no effect on the program execution. For example, you may want to explain how a particular piece of code works. Naturally, you don't want this explanation to execute or to show in the browser. Such explanation is inserted as a comment in the vicinity of the code it explains.

There are single-line and multi-line comments. A single line comment starts with two slashes (like in C++) or with the pound sign (like in Linux). Everything following these characters is disregarded by the interpreter and treated as a comment. For example:

<?php
 # This is a comment
 //This is also a comment
 This is code//But this is a comment
?>