November 2003Bent Thomsen - FIT 6-11 IT – som værktøj Bent Thomsen Institut for Datalogi Aalborg Universitet

November 2003Bent Thomsen - FIT 6-12 Introduction to PHP Bent Thomsen

November 2003Bent Thomsen - FIT 6-13 What is PHP? PHP is a generalized Open Source Server Side Scripting Language that generates HTML content PHP: Recursive Acronym for –PHP: Hypertext Preprocessor PHP was created by Rasmus Lerdorf in 1994 as a tool for Web Development PHP is simple for beginners, yet a powerful tool for the professional Web Developer

November 2003Bent Thomsen - FIT 6-14 Embedding PHP in HTML is different from writing a script or program in other languages like Perl, Java or C#, but similar to JavaScript Instead of writing a program with lots of commands to output HTML, you write an HTML script with some embedded code to do something (in the example on the next page, to output some text). The PHP code is enclosed in start and end tags that allow you to jump into and out of "PHP mode". An example follows

November 2003Bent Thomsen - FIT 6-15 Embedding PHP in HTML A PHP Example First PhP Script <?PHP print(“Hello World”); ?>

November 2003Bent Thomsen - FIT 6-16 PHP Structures A PHP script begins (and ends) with a tag that inform the Web server that it is dealing with a PHP program. This tag is represented as –Alternatively, you can use: … A PHP script is save as a *.php file

November 2003Bent Thomsen - FIT 6-17 Continue … Every script-line must ends with a semi- colon (;) Documentation can be added using the “//” or “/* … */” comment tags –“ // ” for single line comment –“ /*…*/ ” for multiple lines comment

November 2003Bent Thomsen - FIT 6-18 PHP Script Example <?php // This is a very simple script that simply // output the sentence “Hello World!” print (“Hello World!”); ?> Opening Tag Comment Closing Tag Semi-colon

November 2003Bent Thomsen - FIT 6-19 PHP Program In general, a program consists of commands and values. –Commands: what the program can do. –Values are the information that commands are performed with. PHP is no exception. e.g. print (“Hello”); This statement performs the print() command using the value “Hello”

November 2003Bent Thomsen - FIT Print() Function Print () is use to send text to the browser. Another function, echo() behaves the same as Print(). Print() can also be use to send HTML formatted text to the browser. –Print(“ Hello World ”);

November 2003Bent Thomsen - FIT PHP vs. JavaScript What distinguishes PHP from client-side JavaScript? PHP code is executed on the server. If you were to have a script similar to the above on your server, the client would receive the results of running that script, with no way to determine what the underlying code may be.

November 2003Bent Thomsen - FIT Client-side execution using JavaScript Web-Server JavaScript WWW Web-Browser HTML Page Web-Client

November 2003Bent Thomsen - FIT Server-side execution using PHP Script Web-ClientWeb-Server PHP Script HTML-Form Submit Form Data Call PHP interpreter Response Web-Browser WWW Reply

November 2003Bent Thomsen - FIT PHP & Web Servers PHP supports most web servers including Apache Microsoft Internet Information Server Personal Web Server Netscape and iPlanet servers Oreilly Website Pro server Caudium, Xitami, OmniHTTPd For most servers PHP has a module, for the others supporting the CGI standard, PHP can work as a CGI processor.

November 2003Bent Thomsen - FIT PHP VARIABLES PHP keeps variables easy to work with Syntax is minimal All PHP variables start with $ Variable names are case sensitive Strings, integers, floating-point, arrays Variables generally come from 3 places –Assigned within a script –Passed from an HTML page –Or from the PHP environment

November 2003Bent Thomsen - FIT PHP VARIABLES PHP does not require explicit variable declarations Use a variable, and it exists! Examples of variable declaration in PHP –$a = “this is a string”; //this is a string –$b = 4; //this is an integer –$c = ; //this is a floating point number –$d = “5”; //this is another string

November 2003Bent Thomsen - FIT PHP Is Flexible $g = $b + $d ; echo $g will print 9 (See Preceding Slide) $m = 7; // $m is an integer $n = 1.732; // $n is double floating point $p = $m + $n; //$p is also a double floating point variable

November 2003Bent Thomsen - FIT The = sign Use = to indicate an assignment statement: –$X = 4; Use = = for comparison: –If($X==4);

November 2003Bent Thomsen - FIT More on Strings $my_name = “Peter”; $statement = “Hello, my name is $my_name”; –This expands the variable $my_name So the Echo $statement; Will print, “Hello, my name is Peter” If you want to include any of the following characters in your string you must first escape each with backslashes “ \ $

November 2003Bent Thomsen - FIT Operators Assignment ( = ) – returns a value equal to the value that was assigned: $a = ($b = 5); Arithmetic: + - * \ % Concatenation: “now”.“one String” Comparison: == != > >= < <= Logical: || or xor && and !

November 2003Bent Thomsen - FIT Operator Presedence (cast) * \ % + - >= == != && || = and xor or Can be changed by using parentheses e.g. 2*5+6 2*(5+6)

November 2003Bent Thomsen - FIT Constants You indicate that a label is to represent a constant by: define(‘CONSTANT_NAME’,value) or define(‘CONSTANT_NAME’,value,true) When the third parameter is present and true then the parameter label can be used in either upper or lower case e. g. define(‘PI’,3.1412,true) defines a constant PI and another pi that both have the value

November 2003Bent Thomsen - FIT Statements Function calls: print(“hello”); Assignment statements: $first = “first one”; If/Then/Else statement: if (expression){ true_part } else { false_part } While statement: while (expression) { repeated_part } For statement: for (init; test; update) { repeated_part }

November 2003Bent Thomsen - FIT If/Then/Else If/Then/Else statement: if (expression){ true_part } else { false_part } Used to conditional execute part of a PhP script The else part is optional Example: if ($num == 1) { $end = “st”; } else if ($num == 2 or $num ==3) { $end = “ed”; } else { $end = “th”; } print (((string)$num).$end);

November 2003Bent Thomsen - FIT While While statement: while (expression) { repeated_part } Loop, that is repeat all the enclosed PhP statements, while the condition is true Example: $count = 0; while ($count ”); $count = $count + 1; }

November 2003Bent Thomsen - FIT For For statement: for (init; test; update) { repeated_part } Execute the init statement, then test the condition; then repeat the loop In the loop, as long as the condition is true, execute the statements in the body; then execute the update statement; then test the condition Example: for ($n = 1; $n ”);}

November 2003Bent Thomsen - FIT Array Examples Creating a simple Array $class = array (“Web Programming II”, “CS463”, “MWF”); Creating an Associative Array $ranks (“first” =>1, “second” =>2, “third” =>3 ); Heterogeneous Array $studentA = array (“StudentA”, “Sr”, 3.4, 103); Printing echo class[2]; // echo out the second element: prints “CS463”; echo ranks[3]; // echo out the third element: prints 3; echo studentA[4]; // echo out the cumulative credits: prints 103;

November 2003Bent Thomsen - FIT Array - multidimensional creating $students = array( array( “StudentA”, “FR”, 3.0), array( “StudentB”, “JR”, 2.8), array( “StudentC”, “SR”, 3.3) ); Printing print $student[2][0]; //prints “StudentC” More sophisticated? $students2 = array( “StudentA” => array( “Year”=>”FR”, “GPA”=>3.0), “StudentB” => array( “Year”=>”JR”, “GPA”=>2.8), “StudentC” => array( “Year”=>”SR”, “GPA”=>3.3) ); Printing print $students2[“StudentB”][“GPA”]; // prints 2.8

November 2003Bent Thomsen - FIT Functions Functions denote actions that can be taken (on your behalf) by php Example print(“This is some text”); Functions can be parts of an expression Functions have one or more arguments (the part inside the parentheses) The values of the arguments are past to the functions that do something with them (“side effects”) A Function may return a value (example shortly)

November 2003Bent Thomsen - FIT More Functions Built-in functions: –print, round, sqrt, cos, rand, … Use defined functions function diff($par1,$par2){ if ($par1 > $par2){ return $par1 - $par2; } else { return $par2 - $par1; }

November 2003Bent Thomsen - FIT An example <?php /* First define functions use them later */ function diff($par1,$par2){ if ($par1 > $par2){ return $par1 - $par2; } else { return $par2 - $par1; } echo “The difference between 5 and 10 is”; echo diff(5,10); ?>