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Lecture 2. PHP (1) : Data Types, Control Structures, Data Structures, String Handling & . Input/Output. Pre-amble (1) Web 1.0. Basic web 1.0 architecture & communication. Pre-amble (2) http request/response cycle. ID: 590060

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Slide1

UFCEUS-20-2 : Web Programming

Lecture 2PHP (1) : Data Types, Control Structures, Data Structures, String Handling & Input/Output

Slide2

Pre-amble (1) Web 1.0

Basic web 1.0 architecture & communication

Slide3

Pre-amble (2) http request/response cycle

Slide4

Pre-amble (3) Web oriented 3-tier architecture

PHP script

Remote services

Web Server (Apache, IIS)

Browser(IE, Chrome,FireFox, Opera)

Desktop (PC or MAC)

Database

Database Server

SQL

HTTP

HTML

Web Service

tables

DHTML

vision

touch

voice

Slide5

PHP Origins

Originally created by

Rasmus

Lerdorf

(born Greenland, educated in Canada) around 1995

PHP originally abbreviated as ‘Personal Home Pages’, now known as ‘PHP Hypertext

Pre-processor

’

Other key developers:

Zeev

Surashi

and

Andi

Gutmans

(Israel) responsible for PHP 3.0 - a complete re-write of the original PHP/F1 engine (1997)

PHP is Open Source software

First version PHP/FI released 1995

PHP 5.0 released July 2004

Current stable version is

5.4.6 (as of August 2012)

PHP version 5.2.4 current at UWE

PHP Version 6 due for release since late 2010 but ??

Slide6

PHP as a scripting language

A scripting language is:often evolved not designedcross-platform since interpreter is easy to portdesigned to support a specific task – PHP Web supportun-typed variables (but values are typed) implicit variable declaration implicit type conversion stored only as script filescompiled on demandmay run on the server (PHP, Perl) or the client (Javascript)What are the potential differences in programming using an interpreted scripting language like PHP in place of a compiled language (e.g. Java in JSP, .NET)?

Slide7

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=6Relational operators are ,< , > == ( not a single equal) Control structures include if (cond) {..} else { }, while (cond) { .. } , for(startcond; increment; endcond) { } 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

C-like language

Slide8

PHP Scripts

every PHP script is a collection of one or more

statements

; these statements appear as a collection of names, numbers and special symbols;

individual statements are terminated by a

semicolon

(;) and blocks of statements are contained within

curly brackets

({ .. });

statements can be

simple

(e.g.

echo

) while others can be

grouped statements

(e.g. the

if { .. }

elseif

{ .. } else { .. }

block)

PHP can use

literal values

such as numbers and blocks of text (e.g.

"some text"

) or give names to specific

expressions

(e.g. variables, functions or classes)

operators are used to

join values

, usually one value to the left of the operator and one to the right (e.g. 9 + 3 )

Slide9

DOCTYPE html><html><?php # declare a variable & assign it a value $name = "Popeye";?><head> <title>PHP Simple Example</title></head><body> Welcome to PHP, <?php echo("$name"); ?>!</body></html>

Simple PHP script example

single line comment, use # or //

ariable ($name) with value assignment (‘Popeye’)

cripting delimiters

all to built-in ‘echo()’ function

iew script

run script

Slide10

Data Types (1)

PHP has eight different data types – 5 basic and 2 composite types and 1 resource type

The 5 basic data types are:

integers

: whole numbers in the range -2,147,483,648 to +2,147,483,647 on 32-bit architecture. Can be octal (prefixed by 0), decimal and hexadecimal (prefixed by 0x)

floating-point

: real or doubles (decimal), can be written using base 10 notation (e.g. 3900 == 3.9e3)

strings

: sequence of characters contained by single (‘..’) or double ("..") quotes. Within double quotes variables are replaced by their values (interpolated). Escape sequences are used to include special characters within double quoted strings (e.g. \" to include a double quote and \\ to include a backslash)

booleans

: the

boolean

data type evaluates to either true or false (e.g. $a == $b will evaluate to true if both variables contain the same value, false otherwise

null

: a special data type that stands for a lack of value. Often used to initialize or reset variables.

Slide11

Data Types (2)

arrays

: are a composite data type that collect values into a list. The values of the array elements can be text, a number or even another array. Arrays can be from 1 to any number of dimensions.

- arrays are referenced using square [ .. ] brackets.

php

$cities[0] = "London";

$cities[1] = "Bath";

$cities[2] = "Bristol";

print ("I live in $cities[2].<

/>\n");

- an array can be indexed using a string value for the index (called associative array or hash) and are useful in situations where there is a need to collect different types of data into one array. (e.g.

userInfo

["name"] = "Kevin";

)

- array elements containing other arrays are used to build multi-dimensional arrays.

php

$modules = array(

"ISD"=>array(

"Joe",

"Tim",

"Mary"

)

"ISDP"=>array(

"Bob",

"Tom",

"Sue"

)

);

print ($modules["ISD"][2]);

Slide12

Data Types (3)

objects

: are another composite data type fully supported by php.

- php supports standard object-oriented (OO) methodologies and techniques such as

inheritance

- the ability to derive new classes from existing ones and inherit or override their attributes and methods.

encapsulation

- the ability to hide data from users of the class (the

public

protected

and

private

keywords.)

special methods

- for instance, code that is automatically run when a object is created (constructor) or destroyed (destructor).

polymorphism

– o

verloading a function so that a function call will behave differently when passed variables of different type.

- a good introducton to OO programming using php can be found at

http://www.slideshare.net/mgirouard/a-gentle-introduction-to-object-oriented-php/

resources

: are a data type that hold handles to external resources such as open files or database connections.

Slide13

Control statements are a means of executing blocks of code depending on one or more conditions.if (expression) {..} : the simple if statement takes the following form – if (expression) { this block gets executed if the expression evaluates to true }if (expression) {..} elseif (expression) {..} else {..} : the compound if statement takes the following form – if (expression1) { this block gets executed if expression1 is true } elseif (expression2) { this block gets executed if expression1 is false and expression2 is true } else { this block gets executed if both expression1 and expression2 are false }? operator : acts as a shortened version of the if {..} statement. It takes the followng form - conditional expression ? true expression : false expression;

Control Structures (1)

Slide14

Control Structures (2)

switch (expression) {case expression .. case expression .. default}

: similar to the

if .. elseif .. else

structure where a single expression is compared to a set of possible values and if a match is made, the block following the match is executed. The

break

statement can be used to jump out of a switch structure. A default expression can be used to execute code if none of the expressions evaluates to true.

Loops – allow for the repetition of blocks of code until a condition is met.

while (expression) {..}

: when first reached the expression is evaluated and if true the block of code following the expression is executed, otherwise the block is skipped. The

break

statement can be used to break out of a while block. The

continue

statement can be used to return control to the beginning of the block.

do {..} while (expression)

: is a way of delaying the decision to execute a code block until the end.

for (initialization; continue; increment) {..}

: used to carry out a block a code a specific number of times.

foreach (array as key=>value) {..}

: provides a formalized method for iterating over arrays.

Slide15

Control Structures (3)

exit

die

and

return

: the

exit

statement is used to stop execution – it is useful when an error occurs and it could be harmful to continue execution;

the

die

statement is similar to exit but can be followed by an expression which is sent to the browser just before the script is aborted, for instance

fopen

("somefile.txt", "r") OR die("Could not open file");

the

return

statement can be used within functions (see following section) but can also be used with the

include

statement. If used within a script, it stops execution within the current script and returns control to the script that made a call to include. That is, when a

include

is used, the included script may return prematurely.

Slide16

PHP Data Structures (1)

arrays

- arrays collect values into lists - individual items (elements) are accessed using an index which can be an integer or a string - you can build arbitrarily complex data structures using arrays within arrays, that is, a value within an array can hold another array (multidimensional array) single dimension arrays - use square brackets [ ] to refer to an element - arrays are treated like normal variables – you can create it at the point of use without having to declare anything first. example: referencing array elements <?php $teacher[0] = "Prakash"; $teacher[1] = "Paul"; $teacher[2] = "Dan"; $teacher[3] = "Chris"; echo ("$teacher[3] teaches DSA). "); ?> Output?

Note: if you leave out the

index number, php will

start at 0 and use consecutive

integers thereafter.

Slide17

php $teacher[] = "Prakash"; $teacher[] = "Paul"; $teacher[] = "Dan"; $teacher[] = "Chris"; $indexCount = count ($teacher); for ($index=0; $index < $indexCount; $index++) { print("Teacher $index is $teacher[$index]. "); }?>

PHP Data Structures (2)

example: counting and accessing values using a loop

arrays (cont.)

un script

Slide18

php //create hash with data $user["Name"] = "Leon Trotsky"; $user["Location"] = "Coyoacan, Mexico City"; $user["Occupation"] = "Revolutionary"; //loop over the values foreach ($user as $key=>$value) { print ("$key is $value "); }?>

PHP Data Structures (3)

arrays (cont.) Associative Arrays (Hashes in Perl, HashMaps in Java)

un script

Slide19

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.

Slide20

Input / Output & Disk Access (1)

Reading and Writing to Files

Communicating with files follows the pattern of opening a stream to a file, reading from or writing to it, and then closing the stream.

fopen

(..) : the

fopen

function opens a file for reading or writing. The function expects the name of a file and a mode e.g.

fopen

("c:/temp/myfile.txt", "r");

which opens a file called myfile.txt in the directory "c:/temp" in the "read" mode

File read/write modes :

r reading only

w write only, create if necessary, discard previous content

a append to file, create if necessary, start writing at end

r+ reading and writing

w+ reading & writing, create if necessary, discard previous content

a+ reading & writing, create if necessary, start writing at end

Slide21

Input / Output & Disk Access (2)

fclose (resource file)

: used to close a file.

feof (resource file)

: as a file is read, php keeps a pointer to the last place in the file read; the feof function returns true if the end of file is reached.

fgetcsv(resource file, integer length, string separator)

: used for reading comma-separated data from a file. The optional separator argument specifies the character to separate fileds’ If left out, a comma is used.

fgets(resource file, integer length)

: returns a string that reads from a file. It will attempt to read as many characters – 1 as specified by the length value. A linebreak character is treated as a stopping point, as is the end of the file.

fwrite(resource file, string data, integer length)

: writes a string to a file. The length argument is optional and sets the number of bytes to write.

Slide22

the exit() and die() functions

both the

exit()

and

die()

statements

terminate the execution of a script. The two statements are equivalent.

a message can be output as the script is terminated e.g.

$filename = '/path/to/data-file';

$file =

fopen

($filename, 'r')

or exit("unable to open file ($filename)");

Slide23

PHP Books

Intermediate :

Nixon, Robin :

Learning PHP, MySQL, JavaScript and CSS: A Step-by-Step Guide to Creating Dynamic Websites

: O'Reilly Media, 2

ed., 2012

Ullman, Larry :

PHP and MySQL for Dynamic Web Sites: Visual QuickPro Guide

: Peachpit Press, 4

ed., 2011

McLaughlin, Brett :

PHP & MySQL: The Missing Manual

: Pogue Press, 2011

Advanced :

Zandstra, Matt :

PHP Objects, Patterns and Practice

, Apress, 3rd ed., 2010

Gogala, Mladen :

Pro PHP Programming

: Apress, 2011

Saray, Aaron :

Professional PHP Design Patterns

: Wrox, 2009

Slide24

On-line Resources

php

home :

http://www.php.net

learning PHP :

php

@ w3 schools

code and examples :

php

extension & application library (pear) :

http://pear.php.net/

resource index :

http://php.resourceindex.com/

weberdev

http://www.weberdev.com/ArticlesSearch/Category/Beginner+Guides

phpexample

http://phpexamples.me/

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