PHP (acronim recursiv pentru "PHP: Hypertext Preprocessor") este un limbaj de scripting de uz general, cu cod-sursă deschis (open source), utilizat pe scară largă, şi care este potrivit în special pentru dezvoltarea aplicaţiilor web şi poate fi integrat în HTML.

Frumos, dar totuşi ce înseamnă aceasta? Un exemplu:

În locul unei mulţimi de comenzi pentru a afişa HTML (cum este cazul în C sau Perl), paginile PHP conţin HTML cu cod-sursă încorporat, care realizează "ceva" (în acest caz, afişează "Salut, sunt un script PHP!"). Codul-sursă PHP este încorporat între nişte instrucţiuni de procesare de început şi de sfârşit speciale <?php şi ?>, care vă permit să intraţi şi să ieşiţi din "modul PHP".

Ceea ce face PHP să difere de un JavaScript de partea clientului este că codul său este executat pe server, generând HTML care este apoi trimis către client. Clientul va primi rezultatele rulării acelui script, fără a putea cunoaşte codul-sursă ce stă la bază. Dumneavoastră chiar puteţi să configuraţi web server-ul să proceseze toate fişierele HTML cu PHP, şi atunci într-adevăr nu va fi nici o modalitate ca utilizatorii să afle ce aveţi ascuns în mânecă.

Cel mai bun lucru la PHP este simplitatea extremă pentru un începător, dar totodată existenţa multor facilităţi avansate pentru un programator profesionist. Să nu vă fie teamă să citiţi lista lungă a facilităţilor PHP. Puteţi să vă implicaţi în scurt timp şi să începeţi a scrie scripturi simple peste câteva ore.

Cu toate că dezvoltarea PHP e axată pe scripting de partea server-ului, puteţi să realizaţi mult mai multe cu el. Citiţi în continuare şi aflaţi mai multe detalii în secţiunea întitulată Ce poate face PHP?, sau treceţi direct la ghidul de utilizare introductiv dacă sunteţi interesat doar de programarea web.

Orice. PHP este axat în principal pe scripting de partea server-ului, deci puteţi realiza cu el orice poate realiza un alt program CGI, cum ar fi colectarea datelor din forme, generarea conţinutului dinamic al paginilor sau trimiterea şi primirea cookies. Dar PHP poate face mult mai multe.

Sunt trei domenii principale, unde scripturile PHP sunt utilizate.

• Scripting de partea serverului. Acesta este cel mai tradiţional şi de bază domeniu al PHP. Aveţi nevoie de trei lucruri pentru ca aceasta să funcţioneze. Analizatorul PHP (în calitate de CGI, sau modul pentru server), un server web şi un navigator web. Trebuie să rulaţi serverul web cu o instalare PHP conectată la el. Puteţi accesa ieşirile programului PHP cu navigatorul web, vizualizând pagina PHP prin server. Toate acestea pot rula pe computerul dumneavoastră de acasă, dacă doar experimentaţi cu programarea în PHP. Citiţi secţiunea cu instrucţiuni de instalare pentru informaţii suplimentare.
• Scripting în linia de comandă. Puteţi să faceţi un script PHP să ruleze fără un server şi navigator web. Aveţi nevoie doar de analizatorul PHP pentru a-l utiliza în acest mod. Acest mod de utilizare este ideal pentru script-uri executate în mod regulat cu cron (pe *nix sau Linux) sau cu Task Scheduler (pe Windows). Aceste script-uri pot fi utilizate de asemenea pentru lucrări simple de procesare a textelor. Citiţi secţiunea despre Utilizarea PHP în linia de comandă pentru informaţii suplimentare.
• Scrierea aplicaţiilor de birou. PHP probabil că nu este cel mai potrivit limbaj pentru a crea o aplicaţie de birou cu o interfaţă grafică a utilizatorului, dar dacă cunoaşteţi PHP foarte bine şi doriţi să utilizaţi unele facilităţi avansate ale PHP în aplicaţii de partea clientului, puteţi să utilizaţi PHP-GTK pentru a scrie asemenea aplicaţii. De asemenea aveţi posibilitatea să scrieţi în acest mod aplicaţii ce vor rula pe mai multe platforme. PHP-GTK este o extensie a PHP, care nu este disponibilă în distributivul de bază. Dacă v-a interesat PHP-GTK, vizitaţi » propriul său website.

PHP poate fi utilizat pe toate sistemele de operare majore, inclusiv Linux, multe variante Unix (inclusiv HP-UX, Solaris şi OpenBSD), Microsoft Windows, Mac OS X, RISC OS şi probabil altele. PHP de asemenea susţine majoritatea server-elor web existente în prezent. Acestea includ Apache, Microsoft Internet Information Server, Personal Web Server, server-ele Netscape şi iPlanet, server-ul Oreilly Website Pro, Caudium, Xitami, OmniHTTPd şi multe altele. Pentru majoritatea server-elor PHP are modulul său, pentru altele susţine standardul CGI, PHP poate lucra în calitate de procesor CGI.

Deci cu PHP aveţi libertatea alegerii sistemului de operare şi a serverului web. Ba chiar mai mult, aveţi posibilitatea să utilizaţi programarea procedurală sau programarea orientată pe obiecte (POO), sau o combinaţie a acestora. Cu toate că în PHP 4 nu sunt implementate toate facilităţile POO, multe biblioteci de cod şi aplicaţii mari (inclusiv biblioteca PEAR) sunt scrise doar utilizând POO. PHP 5 repară toate deficienţele PHP 4, ce se referă la POO şi prezintă un model obiect-orientat deplin.

Cu PHP nu sunteţi limitat doar la afişarea HTML. Posibilităţile PHP permit de a afişa imagini, fişiere PDF şi chiar filme Flash (utilizând libswf şi Ming) generate "din zbor". Puteţi de asemenea cu uşurinţă să afişaţi orice text, cum ar fi XHTML sau alt fişier XML. PHP poate genera automat aceste fişiere şi le poate salva în sistemul de fişiere, în loc să le afişeze, formând astfel un sistem de cache al conţinutului dinamic de partea server-ului.

Una dintre cele mai puternice şi semnificative facilităţi ale PHP este susţinerea unui larg domeniu de baze de date. Scrierea unei pagini web cu susţinerea bazelor de date este incredibil de simplă. Următoarele baze de date sunt susţinute în prezent:

• Adabas D
• dBase
• Empress
• FilePro (numai citire)
• Hyperwave
• IBM DB2
• Informix
• Ingres
• InterBase
• FrontBase
• mSQL
• Direct MS-SQL
• MySQL
• ODBC
• Oracle (OCI7 şi OCI8)
• Ovrimos
• PostgreSQL
• SQLite
• Solid
• Sybase
• Velocis
• Unix dbm

PHP de asemenea poate să "converseze" cu alte servicii utilizând protocoale cum ar fi LDAP, IMAP, SNMP, NNTP, POP3, HTTP, COM (pe Windows) şi multe altele. Puteţi de asemenea să deschideţi socket-uri de reţea "crude" şi să interacţionaţi utilizând orice alt protocol. PHP susţine WDDX - schimbul de date complexe între aproape toate limbajele de programare web. Vorbind despre interconectare, PHP susţine instanţierea obiectelor Java şi utilizarea lor transparentă ca obiecte PHP. Puteţi de asemenea să utilizaţi extensia CORBA pentru a accesa obiecte la distanţă.

PHP posedă facilităţi foarte utile de procesare a textelor, de la expresii regulare POSIX Extended sau Perl până la analiza documentelor XML. Pentru analiza şi accesarea documentelor XML, PHP 4 susţine standardele SAX şi DOM, şi pentru transformarea documentelor XML puteţi utiliza extensia XSLT. PHP 5 standardizează toate extensiile XML pe baza solidă a libxml2 şi extinde setul de facilităţi prin adăugarea susţinerii SimpleXML şi XMLReader.

Şi, în sfârşit, avem multe alte extensii interesante: funcţii ale motoarelor de căutare mnoGoSearch, funcţii IRC Gateway, multe utilitare de compresie (gzip, bz2, zip), conversii calendaristice, traduceri...

După cum puteţi vedea, această pagină nu este suficientă pentru a evidenţia toate facilităţile şi beneficiile oferite de PHP. Citiţi în continuare secţiunile despre instalarea PHP şi accesaţi referinţele funcţiilor pentru a găsi explicaţiile extensiilor menţionate anterior.

In this tutorial we assume that your server has activated support for PHP and that all files ending in .php are handled by PHP. On most servers, this is the default extension for PHP files, but ask your server administrator to be sure. If your server supports PHP, then you do not need to do anything. Just create your .php files, put them in your web directory and the server will automatically parse them for you. There is no need to compile anything nor do you need to install any extra tools. Think of these PHP-enabled files as simple HTML files with a whole new family of magical tags that let you do all sorts of things. Most web hosts offer PHP support, but if your host does not, consider reading the » PHP Links section for resources on finding PHP enabled web hosts.

Let us say you want to save precious bandwidth and develop locally. In this case, you will want to install a web server, such as » Apache, and of course » PHP. You will most likely want to install a database as well, such as » MySQL.

You can either install these individually or choose a simpler way. Our manual has installation instructions for PHP (assuming you already have some web server set up). In case you have problems with installing PHP yourself, we would suggest you ask your questions on our » installation mailing list. If you choose to go on the simpler route, then » locate a pre-configured package for your operating system, which automatically installs all of these with just a few mouse clicks. It is easy to setup a web server with PHP support on any operating system, including MacOSX, Linux and Windows. On Linux, you may find » rpmfind and » PBone helpful for locating RPMs. You may also want to visit » apt-get to find packages for Debian.

Create a file named hello.php and put it in your web server's root directory (DOCUMENT_ROOT) with the following content:

<html>
 <head>
  <title>PHP Test</title>
 </head>
 <body>
 <p>Hello World</p>
 </body>
</html>

     

This program is extremely simple and you really did not need to use PHP to create a page like this. All it does is display: Hello World using the PHP echo() statement. Note that the file does not need to be executable or special in any way. The server finds out that this file needs to be interpreted by PHP because you used the ".php" extension, which the server is configured to pass on to PHP. Think of this as a normal HTML file which happens to have a set of special tags available to you that do a lot of interesting things.

If you tried this example and it did not output anything, it prompted for download, or you see the whole file as text, chances are that the server you are on does not have PHP enabled, or is not configured properly. Ask your administrator to enable it for you using the Installation chapter of the manual. If you are developing locally, also read the installation chapter to make sure everything is configured properly. Make sure that you access the file via http with the server providing you the output. If you just call up the file from your file system, then it will not be parsed by PHP. If the problems persist anyway, do not hesitate to use one of the many » PHP support options.

The point of the example is to show the special PHP tag format. In this example we used <?php to indicate the start of a PHP tag. Then we put the PHP statement and left PHP mode by adding the closing tag, ?>. You may jump in and out of PHP mode in an HTML file like this anywhere you want. For more details, read the manual section on the basic PHP syntax.

Notă: A Note on Line Feeds Line feeds have little meaning in HTML, however it is still a good idea to make your HTML look nice and clean by putting line feeds in. A linefeed that follows immediately after a closing ?> will be removed by PHP. This can be extremely useful when you are putting in many blocks of PHP or include files containing PHP that aren't supposed to output anything. At the same time it can be a bit confusing. You can put a space after the closing ?> to force a space and a line feed to be output, or you can put an explicit line feed in the last echo/print from within your PHP block.

Notă: A Note on Text Editors There are many text editors and Integrated Development Environments (IDEs) that you can use to create, edit and manage PHP files. A partial list of these tools is maintained at » PHP Editors List. If you wish to recommend an editor, please visit the above page and ask the page maintainer to add the editor to the list. Having an editor with syntax highlighting can be helpful.

Notă: A Note on Word Processors Word processors such as StarOffice Writer, Microsoft Word and Abiword are not optimal for editing PHP files. If you wish to use one for this test script, you must ensure that you save the file as plain text or PHP will not be able to read and execute the script.

Notă: A Note on Windows Notepad If you are writing your PHP scripts using Windows Notepad, you will need to ensure that your files are saved with the .php extension. (Notepad adds a .txt extension to files automatically unless you take one of the following steps to prevent it.) When you save the file and are prompted to provide a name for the file, place the filename in quotes (i.e. "hello.php"). Alternatively, you can click on the 'Text Documents' drop-down menu in the 'Save' dialog box and change the setting to "All Files". You can then enter your filename without quotes.

Now that you have successfully created a working PHP script, it is time to create the most famous PHP script! Make a call to the phpinfo() function and you will see a lot of useful information about your system and setup such as available predefined variables, loaded PHP modules, and configuration settings. Take some time and review this important information.

Let us do something more useful now. We are going to check what sort of browser the visitor is using. For that, we check the user agent string the browser sends as part of the HTTP request. This information is stored in a variable. Variables always start with a dollar-sign in PHP. The variable we are interested in right now is $_SERVER['HTTP_USER_AGENT'].

Notă: $_SERVER is a special reserved PHP variable that contains all web server information. It is known as a superglobal. See the related manual page on superglobals for more information. These special variables were introduced in PHP » 4.1.0. Before this time, we used the older $HTTP_*_VARS arrays instead, such as $HTTP_SERVER_VARS. Although deprecated, these older variables still exist. (See also the note on old code.)

To display this variable, you can simply do:

Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
    

There are many types of variables available in PHP. In the above example we printed an Array element. Arrays can be very useful.

$_SERVER is just one variable that PHP automatically makes available to you. A list can be seen in the Reserved Variables section of the manual or you can get a complete list of them by looking at the output of the phpinfo() function used in the example in the previous section.

You can put multiple PHP statements inside a PHP tag and create little blocks of code that do more than just a single echo. For example, if you want to check for Internet Explorer you can do this:

You are using Internet Explorer.<br />

     

Here we introduce a couple of new concepts. We have an if statement. If you are familiar with the basic syntax used by the C language, this should look logical to you. Otherwise, you should probably pick up an introductory PHP book and read the first couple of chapters, or read the Language Reference part of the manual.

The second concept we introduced was the strpos() function call. strpos() is a function built into PHP which searches a string for another string. In this case we are looking for 'MSIE' (so-called needle) inside $_SERVER['HTTP_USER_AGENT'] (so-called haystack). If the needle is found inside the haystack, the function returns the position of the needle relative to the start of the haystack. Otherwise, it returns FALSE. If it does not return FALSE, the if expression evaluates to TRUE and the code within its {braces} is executed. Otherwise, the code is not run. Feel free to create similar examples, with if, else, and other functions such as strtoupper() and strlen(). Each related manual page contains examples too. If you are unsure how to use functions, you will want to read both the manual page on how to read a function definition and the section about PHP functions.

We can take this a step further and show how you can jump in and out of PHP mode even in the middle of a PHP block:

<h3>strpos() must have returned non-false</h3>
<p>You are using Internet Explorer</p>

     

Instead of using a PHP echo statement to output something, we jumped out of PHP mode and just sent straight HTML. The important and powerful point to note here is that the logical flow of the script remains intact. Only one of the HTML blocks will end up getting sent to the viewer depending on the result of strpos(). In other words, it depends on whether the string MSIE was found or not.

One of the most powerful features of PHP is the way it handles HTML forms. The basic concept that is important to understand is that any form element will automatically be available to your PHP scripts. Please read the manual section on Variables from external sources for more information and examples on using forms with PHP. Here is an example HTML form:

<form action="action.php" method="post">
 <p>Your name: <input type="text" name="name" /></p>
 <p>Your age: <input type="text" name="age" /></p>
 <p><input type="submit" /></p>
</form>

There is nothing special about this form. It is a straight HTML form with no special tags of any kind. When the user fills in this form and hits the submit button, the action.php page is called. In this file you would write something like this:

Hi Joe. You are 22 years old.

     

Apart from the htmlspecialchars() and (int) parts, it should be obvious what this does. htmlspecialchars() makes sure any characters that are special in html are properly encoded so people can't inject HTML tags or Javascript into your page. For the age field, since we know it is a number, we can just convert it to an integer which will automatically get rid of any stray characters. You can also have PHP do this for you automatically by using the filter extension. The $_POST['name'] and $_POST['age'] variables are automatically set for you by PHP. Earlier we used the $_SERVER superglobal; above we just introduced the $_POST superglobal which contains all POST data. Notice how the method of our form is POST. If we used the method GET then our form information would live in the $_GET superglobal instead. You may also use the $_REQUEST superglobal, if you do not care about the source of your request data. It contains the merged information of GET, POST and COOKIE data. Also see the import_request_variables() function.

You can also deal with XForms input in PHP, although you will find yourself comfortable with the well supported HTML forms for quite some time. While working with XForms is not for beginners, you might be interested in them. We also have a short introduction to handling data received from XForms in our features section.

Now that PHP has grown to be a popular scripting language, there are a lot of public repositories and libraries containing code you can reuse. The PHP developers have largely tried to preserve backwards compatibility, so a script written for an older version will run (ideally) without changes in a newer version of PHP. In practice, some changes will usually be needed.

Two of the most important recent changes that affect old code are:

• The deprecation of the old $HTTP_*_VARS arrays (which need to be indicated as global when used inside a function or method). The following superglobal arrays were introduced in PHP » 4.1.0. They are: $_GET, $_POST, $_COOKIE, $_SERVER, $_FILES, $_ENV, $_REQUEST, and $_SESSION. The older $HTTP_*_VARS arrays, such as $HTTP_POST_VARS, also exist. Începând cu PHP 5.0.0 variabilele predefinite cu tablourile lungi pot fi dezactivate cu ajutorul directivei register_long_arrays.
• External variables are no longer registered in the global scope by default. In other words, as of PHP » 4.2.0 the PHP directive register_globals is off by default in php.ini. The preferred method of accessing these values is via the superglobal arrays mentioned above. Older scripts, books, and tutorials may rely on this directive being on. If it were on, for example, one could use $id from the URL http://www.example.com/foo.php?id=42. Whether on or off, $_GET['id'] is available.

With your new knowledge you should be able to understand most of the manual and also the various example scripts available in the example archives. You can also find other examples on the php.net websites in the links section: » http://www.php.net/links.php.

To view various slide presentations that show more of what PHP can do, see the PHP Conference Material Site: » http://talks.php.net/