Ravensky - PHP: Full Guide

Contents:

Part I. What is the web programming. Main technologies

Part 2. PHP: Hypertext preprocessor

Part 3. PHP installation

Part 4. Apache+PHP configuration

Part 5. PHP5 installation

Welcome to the world of web programming! During this course I will try to teach you, and you, in turn, will try to learn to create various Web applications, from elementary examples, to full-function products.

At once I will notice that I write, calculating that you know bases of a markup language of HTML and you have at least brief experience of programming. Otherwise... well you understood.

But, before to begin studying directly of the PHP language, let's understand that such web programming.

I. What is the web programming. Main technologies

I-1. Client-server

If you already tried (and can be, even it is not unsuccessful) to program, for example, on Delphi, either Visual Basic, or even the Visual C ++, then got used to such scheme of a program runtime: the button is clicked - the code is carried out - the result is displayed, and all this is carried out on one computer.

In web programming everything is in a different way.

You thought what occurs when you enter in an address bar of the URL browser (Universal Resource Location, or in a popular speech - the address)? Scheme of work following:

The browser opens connection with the server

The browser sends the server a request for obtaining the page

The server creates the answer (most often - a HTML code) to the browser and closes connection

The browser processes a HTML code and displays the page

Pay attention on highlighted in bold. Still before you saw the requested page on the screen, connection with the server is closed, and he forgot about you. And when you will enter another (or the same) the address, or click on the link, or you will press the HTML forms button - the same scheme will repeat again.

Such scheme of work call "client-server". The client in this case - the browser.

So, connection with the Web server lasts only several seconds (or a share of seconds) is a period between click on the link (or in a different way a request) and the beginning of page display. The majority of browsers during connection time display a certain indicator, for example, MS Internet Explorer displays animation in the upper right corner.

The attentive reader can notice here - and how so, I already read the page, and the indicator still shows connection process? The matter is that tag (loading of the image) and some other are no more than one more server request - and it is carried out just as also any other - according to the same scheme. And the picture request, from the point of view of the server, is completely independent of a HTML nickname request.

Forever to get rid of HTTP perception as "a black box", "we will pretend to be" the browser by means of telnet:

Let's start telnet www.php5.com 80

Let's enter in a terminal window the following (if input is not displayed - nothing terrible):

GET/HTTP/1.0 [we will click Enter here]

Host: www.php5.com [we will click Enter twice here]

Clicking of Enter corresponds, as a rule, to a combination of characters of CR + LF designated as \by r\n. This designation will be used further.

On the screen will run a http://www.php5.com/ page HTML code. As you can see - anything difficult.

The source code of the current page can be browsed practically in any browser, having selected in the View|Source menu.

Pictures, frames - all this additional requests, just the same. Actually, from where pictures in a browser window undertake: when parsing (processing) of a HTML code, the browser, stumble on a tag makes additional server request - a picture request, and displays it on site where there is a tag .

Try:

telnet www.php5.com 80

GETphp/php5com.png HTTP/1.0\r\n

Host: www.php5.com\r\n\r\n

On the screen will run what you will see if you browse this png-file in a text editor.

I-2. HTML forms. Methods of sending data for the server

You for certain already met HTML forms:

Enter your name:

Having saved this code in the HTML file and having browsed it by means of your favourite browser, you will see a usual HTML form:

Beginning of a form

Enter your name:

End of a form

Let's consider the tags used in this small example in more detail.

The tag

having pair ending tag , actually also sets a form. Its attributes - both are optional:

action - specifies URL (full or relative) to which the form will be sent. Sending a form is the same server request, as well as all others (as I already described above).

If not to specify this attribute, the majority of browsers (more precisely, all browsers known to me) send a form to the current document, that is "to themselves". This convenient reduction, but according to the action HTML attribute standard it is obligatory.

method - a way of sending a form. They are two.

o GET - sending this form in an address bar.

You could notice presence at the end of URL of the character on the different websites "?" and the following data behind it in a format parameter = value. Here "parameter" corresponds to value of name attribute of elements of a form (see below about a tag ), and "value" - to value attribute contents (it, for example, contains input of the user in a text box of the same tag ).

For an example - try to look for something in Google and pay attention to an address bar of the browser. It is also the way GET.

o POST - these forms go in a request body. If it is not absolutely clear (or it is absolutely unclear) what is it - do not worry, we will return to this question soon.

If the method attribute is not specified - "GET" is meant.

The tag - sets the form element determined by type attribute:

text Value sets an input single-line text box

submit Value sets the button when which clicking there is a sending a form for the server

Also other values are possible (and - not the only tag setting a form element), but we will consider them in the following chapters.

So, what occurs when we click OK?

The browser browses the elements incoming a form and creates these forms of their name and value attributes. The name Bryan is Let's say entered. In this case these forms - name=Bryan&okbutton=OK

The browser establishes connection with the server, sends a request of the document specified in action attribute of a tag

for the server, using the method of sending data specified in method attribute (in this case - GET), transferring these forms in a request.

The server analyzes the received request, creates the answer, sends it to the browser and closes connection

The browser displays the document received from the server

Sending the same request manually (with the help of telnet) looks as follows (we will assume that domain name of the website - www.example.com):

telnet www.example.com 80

GET /cgi-bin/form_handler.cgi?name=Bryan&okbutton=OK HTTP/1.0\r\n

Host: www.example.com\r\n

\r\n

As you, most likely, already guessed, clicking of the submit-button in shape with method of sending "GET" is similar to input of the relevant URL (a signed question and data of a form at the end) in an address bar of the browser: http://www.example.com/cgi-bin/form_handler.cgi?name=Bryan&okbutton=OK

Actually, the GET method is used always when you request any document from the server, having just entered its URL, or having clicked on the link. When using

, the question mark and these forms are just added to URL.

Perhaps, all these technical details and exercises from telnet-ohms seem to you incredibly boring and even unnecessary ("and at what here PHP?"). And in vain. These are the basics under the HTTP protocol which each Web programmer needs to know by heart, and it is not theoretical knowledge - all this is useful in practice.

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