Introduction to PHP

PHP PHP is the Hypertext Pre-processor –Script language –Embedded into HTML –Runs as Apache module –Can use DB (MySQL, Oracle, Microsoft SQL, PostgreSQL) –Rich features: XML, PDF, IMAP, LDAP

PHP Origins Rasmus LerdorfRasmus Lerdorf (born Greenland, ed Canada) PHP originally abbreviates for ‘Personal Home Pages’, now ‘PHP Hypertext Processor’ Other key developers: Zeev Surashi and Andi Gutmans (Israel) Open Source PHPPHP version current at UWE Due to upgrade to PHP 5

Scripting languages A scripting language is: –often evolved not designed –cross-platform since interpreter is easy to port –designed to support a specific task – PHP -> Web support –un-typed variables (but values are typed) –implicit variable declaration –implicit type conversion –stored only as script files –compiled on demand –may run on the server (PHP) or the client (Javascript)

PHP details Procedural language –Compare with Javascript which is event-driven C-like syntax - { } ; Extensive Function Library Good Web-server integration –Script embedded in HTML –Easy access to form data and output of HTML pages Not fully object-oriented –Java is fully object oriented – all functions have to be in a class –In PHP, classes are additional but quite simple to use

PHP and HTML HTML-embedded –PHP scripts are essentially HTML pages with the occasional section of PHP script. – PHP script is enclosed in the tag pair:

Free format - white space is ignored Statements are terminated by semi-colon ; Statements grouped by { … } Comments begin with // or a set of comments /* */ Assignment is ‘=’ $a=6 Relational operators are, == ( not a single equal) Control structures include if (cond) {..} else { }, while (cond) {.. }, for(startcond; increment; endcond) { } C-like language

Arrays are accessed with [ ] : $x[4] is the 5th element of the array $x – indexes start at 0 Associative Arrays (hash array in Perl, dictionary in Java) are accessed in the same way: $y[“fred”] Functions are called with the name followed by arguments in a fixed order enclosed in ( ) : substr(“fred”,0,2) Case sensitive - $fred is a different variable to $FRED

Function library Basic tasks –String Handling –Mathematics – random numbers, trig functions.. –Regular Expressions –Date and time handling –File Input and Output And more specific functions for- –Database interaction – MySQL, Oracle, Postgres, Sybase, MSSQL.. –Encryption –Text translation –Image creation –XML

String Handling String literals (constants) enclosed in double quotes “ ” or single quotes ‘ ’ Within “”, variables are replaced by their value: – called variable interpolation. “My name is $name, I think” Within single quoted strings, interpolation doesn’t occur Strings are concatenated (joined end to end) with the dot operator “key”.”board” == “keyboard”

Standard functions exist: strlen(), substr() etc Values of other types can be easily converted to and from strings – numbers implicitly converted to strings in a string context. Regular expressions be used for complex pattern matching.

Learning PHP Start with just the basics, installing a script to output an HTML page Understand how PHP supports interaction with the Browser or other clients Understand how PHP supports integration with databases – Postgress

Basic PHP Syntax

Datatypes String –'My name is Taro Keio.' –"My name is $name." Boolean –true –false Integer –100 –0x1c Floating point Array –array("tokyo", "hanoi", "london") –array("japan" => "tokyo", "vietnam" => "hanoi", "england" => "london") –$a[2] –$a["vietnam"]

Variables in PHP All variables in PHP start with a $ sign symbol. Variables may contain strings, numbers, or arrays.

Variable Naming Rules A variable name must start with a letter or an underscore "_" A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ ) A variable name should not contain spaces. If a variable name should be more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)

Comments in PHP <?php //This is a comment /*This is a comment block*/ ?>

The If...Else Statement Syntax if (condition) code to be executed if condition is true; else code to be executed if condition is false;

Example <?php $d=date("D"); if ($d=="Fri") echo "Have a nice weekend!"; else echo "Have a nice day!"; ?>

The Switch Statement Syntax switch (expression) { case label1: code to be executed if expression = label1; break; case label2: code to be executed if expression = label2; break; default: code to be executed if expression is different from both label1 and label2; }

Looping while - loops through a block of code if and as long as a specified condition is true do...while - loops through a block of code once, and then repeats the loop as long as a special condition is true for - loops through a block of code a specified number of times foreach - loops through a block of code for each element in an array

The while Statement Syntax while (condition) code to be executed;

The do...while Statement Syntax Do { code to be executed; } while (condition);

The for Statement Syntax for (initialization; condition; increment) { code to be executed; }

The foreach Statement Syntax foreach (array as value) { code to be executed; }

PHP Function <?php function writeMyName() { echo "Kai Jim Refsnes"; } writeMyName(); ?>

PHP Form Handling Name: Age:

welcome.php Welcome. You are years old.