Introduction to PHP

1. Introduction to PHP Basic principles and syntax CSI 4118 -- University of Ottawa

2. What is PHP? • PHP == ‘Hypertext Preprocessor’ • Open-source, server-side scripting language • Used to generate dynamic web-pages • PHP scripts reside between reserved PHP tags • This allows the programmer to embed PHP scripts within HTML pages CSI 4118 – University of Ottawa

3. What is PHP (cont’d) • Interpreted language, scripts are parsed at run-time rather than compiled beforehand • Executed on the server-side • Source-code not visible by client • ‘View Source’ in browsers does not display the PHP code • Plethora of built-in functions allow for fast development • Compatible with many popular databases CSI 4118 – University of Ottawa

4. What does PHP code look like? • Structurally similar to C/C++ • Supports procedural and object-oriented paradigm (to some degree) • All PHP statements end with a semi-colon • Each PHP script must be enclosed in the reserved PHP tag <?php …?> CSI 4118 – University of Ottawa

5. Comments in PHP • Standard C, C++, and shell comment symbols // C++ and Java-style comment # Shell-style comments /* C-style comments These can span multiple lines */ CSI 4118 – University of Ottawa

6. Variables in PHP • PHP variables must begin with a “$” sign • Case-sensitive ($Foo != $foo != $fOo) • Global and locally-scoped variables • Global variables can be used anywher • Local variables restricted to a function or class • Certain variable names reserved by PHP • Form variables ($_POST, $_GET) • Server variables ($_SERVER) • Etc. CSI 4118 – University of Ottawa

7. Variable usage <?php $foo = 25; // Numerical variable$bar = “Hello”; // String variable $foo = ($foo * 7); // Multiplies foo by 7$bar = ($bar * 7); // Invalid expression ?> CSI 4118 – University of Ottawa

8. Echo • The PHP command ‘echo’ is used to output the parameters passed to it • The typical usage for this is to send data to the client’s web-browser • Syntax • void echo (string arg1 [, string argn...]) • In practice, arguments are not passed in parentheses since echo is a language construct rather than an actual function CSI 4118 – University of Ottawa

9. Echo example <?php $foo = 25; // Numerical variable$bar = “Hello”; // String variable echo $bar; // Outputs Hello echo $foo,$bar; // Outputs 25Hello echo “5x5=“,$foo; // Outputs 5x5=25 echo “5x5=$foo”; // Outputs 5x5=25echo ‘5x5=$foo’; // Outputs 5x5=$foo ?> • Notice how echo ‘5x5=$foo’ outputs $foo rather than replacing it with 25 • Strings in single quotes (‘ ‘) are not interpreted or evaluated by PHP • This is true for both variables and character escape-sequences (such as “\n” or “\\”) CSI 4118 – University of Ottawa

10. Functions • Functions MUST be defined before then can be called • Function headers are of the format • Note that no return type is specified • Unlike variables, function names are not case sensitive (foo(…) == Foo(…) == FoO(…)) function functionName($arg_1, $arg_2, …, $arg_n) CSI 4118 – University of Ottawa

11. Functions example <?php // This is a function function foo($arg_1, $arg_2) { $arg_2 = $arg_1 * $arg_2;   return $arg_2;} $result_1 = foo(12, 3); // Store the function echo $result_1; // Outputs 36 echo foo(12, 3); // Outputs 36 ?> CSI 4118 – University of Ottawa

12. The Big Picture for Assignment 2 • Learn about web-servers • Learn about Apache • Download / Installation • Learn about PHP • Download / Installation • Configure Apache • Modify and save the configuration file, then restart • Learn about file I/O without the aid of SQL • Design, write, and test scripts to solve Assignment 2 CSI 4118 – University of Ottawa

13. Saving Data in Text Files • PHP has built in functions for File I/O processing • fopen (..), fwrite(..), fclose(..), fflush(..), file_get_contents(..) • Using these pre-made functions, File I/O in PHP is similar to that of C • General Flow: • Open file • Read data • Modify data • Write data • Close file CSI 4118 – University of Ottawa

14. Saving Data in Text Files: Example <?php$filename = 'test.txt'; /* Filename for writing. This is assumed to be in the same directory as the script */$somecontent = "Add this to the file\n"; // String to append to the file// Let's make sure the file exists and is writable first.if (is_writable($filename)) { // Open the file in append mode ( ‘a’ ) so that the string being stored is written at the end of the // file rather than replacing the existing text    if (!$handle = fopen($filename, 'a')) {         echo "Cannot open file ($filename)";         exit;   }   // Write $somecontent to the opened file.   if (fwrite($handle, $somecontent) === FALSE) {       echo "Cannot write to file ($filename)";       exit;   }   echo "Success, wrote ($somecontent) to file ($filename)";   fclose($handle);} else {   echo "The file $filename is not writable";} ?> CSI 4118 – University of Ottawa

15. For more information… • http://www.php.net/manual/en/ • http://www.w3schools.com/php/default.asp • http://www.zend.com/zend/tut/ CSI 4118 – University of Ottawa

16. Various Notes on PHP Several useful tidbits CSI 4118 -- University of Ottawa

17. Header • The PHP function header(string)is used to send a raw HTTP header to the browser • Most useful for redirecting the browser to another page (after a successful login, for example) <?php // string storing the destination $url = http://www.uottawa.ca /* Sends a header telling the browser to navigate to $url */ header(“Location: “ . $url); ?> CSI 4118 – University of Ottawa

18. IMPORTANT NOTE! It is absolutely vital that any calls to header(…) must be made before any other output is sent to the browser (either by standard HTML tags, HTML comments, PHP’s echo command, or even blank lines. Failure to ensure this will result in an error when your PHP script runs CSI 4118 – University of Ottawa

19. Preventing Browser-caching • The header(…) function can also be used to prevent the browser from caching the data sent by PHP. This forces the browser to refresh the page everytime the page is loaded. CSI 4118 – University of Ottawa

20. Anti-caching example <?php// Date in the pastheader("Expires: Mon, 26 Jul 1997 05:00:00 GMT");// always modifiedheader("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");// HTTP/1.1header("Cache-Control: no-store, no-cache, must-revalidate");header("Cache-Control: post-check=0, pre-check=0", false);// HTTP/1.0header("Pragma: no-cache");?> CSI 4118 – University of Ottawa

21. MD5 Hashing • The PHP Function md5(string) takes a string parameter and returns the md5 hash of that string (a 32-bit hexadecimal number) • This function does not encrypt the data sent to it, it merely returns a hash-value for that data. <?php $password = ‘tomatePotate'; if (md5($password) === /*MD5 of password stored in file*/) { echo “The passwords match!” } ?> CSI 4118 – University of Ottawa

22. Resources • PHP function header(…)http://www.php.net/manual/en/function.header.php • PHP function md5(…) http://www.php.net/manual/en/function.md5.php • RSA MD5 Message Digest Algorithmhttp://www.faqs.org/rfcs/rfc1321 CSI 4118 – University of Ottawa

23. PHP the [Easy] way A simple way to configure PHP and Apache for Assignment 2 CSI 4118 -- University of Ottawa

24. Configuration woes… • For various reasons, manually configuring PHP to work with Apache can present a great deal of trouble • There exists an elegant software package which is designed to abstract the configuration process from web-developers CSI 4118 – University of Ottawa

25. [Easy]PHP • http://www.easyphp.org/ • Automagically installs and configures Apache, PHP, and MySQL • Defaults to running from http://localhost/ • Installer: • http://www.easyphp.org/telechargements/dn.php?F=easyphp1-7 • English Readme files (Extract to EasyPHP Installation Directory): • http://www.easyphp.org/telechargements/dn.php?F=indexUS_1.7 CSI 4118 – University of Ottawa