lecture 3 PHP

8/7/2019 lecture 3 PHP

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What is PHPWhat is PHP??

y PHP stands for PHP: Hypertext Preprocessory PHP is a server-side scripting language, like

ASP

y PHP scripts are executed on the servery PHP supports many databases (MySQL,

Informix, Oracle, Sybase, Solid, PostgreSQL,

Generic ODBC, etc.)y PHP is an open source software

y PHP is free to download and use


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What is a PHP FileWhat is a PHP File??

y PHP files can contain text, HTML tags and

scripts

y PHP files are returned to the browser as

plain HTML

y PHP files have a file extension of ".php",".php3", or ".phtml"


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Why PHP?Why PHP?

y PHP runs on different platforms

(Windows, Linux, Unix, etc.)

y PHP is compatible with almost all servers

used today (Apache, IIS, etc.)

y PHP is FREE to download from the officialPHP resource: www.php.net

y PHP is easy to learn and runs efficientlyon the server side


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PHPPHP SyntaxSyntax

y PHP code is executed on the server, and the

plain HTML result is sent to the browser.

y

A PHP scripting block always startswith . A PHP scriptingblock can be placed anywhere in the

document.

y On servers with shorthand support enabled

you can start a scripting block with .


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ThereThere areare twotwo basicbasic statementsstatements toto outputoutput texttext withwith

PHPPHP:: echoecho andand printprint.. InIn thethe exampleexample aboveabove wewe havehave usedusedthethe echoecho statementstatement toto outputoutput thethe texttext "Hello"Hello World"World"..

//hellow


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Naming Rules forNaming Rules forVariablesVariables

y

A variable name must start with a letter or anunderscore "_"

y A variable name can only contain alpha-

numeric characters and underscores (a-z, A-Z,0-9, and _ )

y A variable name should not contain spaces. If avariable name is more than one word, it

should be separated with an underscore($my_string), or with capitalization

($myString)


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StringVariables inStringVariables in PHPPHP

y String variables are used for values thatcontains characters.

y In this chapter we are going to look at themost common functions and operators usedto manipulate strings in PHP.

y After we create a string we can manipulateit. A string can be used directly in a functionor it can be stored in a variable.

y


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The ConcatenationThe Concatenation OperatorOperator

y The concatenation operator (.) is used to

put two string values together.

y


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TheThe strlenstrlen()() functionfunction

y

y The strpos() function is used to search forcharacter within a string.

y If a match is found, this function will returnthe position of the first match. If no match isfound, it will return FALSE.

y


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PHPPHP OperatorsOperators

Operator Description Example Result

+ Addition x=2x+2

4

- Subtraction x=2

5-x

3

* Multiplication x=4x*5

20

/ Division 15/55/2

32.5

% Modulus (division remainder) 5%210%810%2

120

++ Increment x=5x++

x=6

-- Decrement x=5x--

x=4


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Assignment operatorsAssignment operators

Operator Example Is The Same As

= x=y x=y

+= x+=y x=x+y

-= x-=y x=x-y

*= x*=y x=x*y

/= x/=y x=x/y

.= x.=y x=x.y

%= x%=y x=x%y


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Comparison and logical operatorsComparison and logical operatorsperator Description Example== is equal to 5==8 returns false

!= is not equal 5!=8 returns true

is not equal 58 returns true

> is greater than 5>8 returns false

< is less than 5= is greater than or equal to 5>=8 returns false


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PHPPHP If...ElseIf...Else StatementsStatements

y The if Statement

y if (condition) code to be executed if condition is true;

y


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The if...elseThe if...else StatementStatementy

if (condition)code to be executed if condition is true;elsecode to be executed if condition is false;

y


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y


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TheThe if...if...elseifelseif....else....else StatementStatementy if (condition)

code to be executed if condition is true;elseif (condition)code to be executed if condition is true;

elsecode to be executed if condition is false;

y


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The PHP SwitchThe PHP Switch StatementStatement

y switch (n){case label1:code to be executed if n=label1;

break;case label2:code to be executed if n=label2;break;

default:code to be executed if n is different from both

label1 and label2;}


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The whileThe while LoopLoopy while (condition)

{code to be executed;}

y


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The do...whileThe do...while StatementStatementy do

{

code to be executed;}

while (condition);

y


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The forThe for LoopLoop

y for (init; condition; increment){code to be executed;}

y


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TheThe foreachforeach looploop is used to loop through arrays.is used to loop through arrays.

y foreach ($arrayas $value){code to be executed;}

y


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PHPPHP ArraysArrays

In PHP, there are three kind of arrays:yNumeric array - An array with a numeric

index

y

Associative

arr

ay - An array where each IDkey is associated with a value

yMultidimensional array - An arraycontaining one or more arrays


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NumericNumeric ArraysArraysy

$cars=array("Saab","Volvo","BMW","Toyota");

y $cars[0]="Saab";$cars[1]="Volvo";$cars[2]="BMW";

$cars[3]="Toyota";y


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AssociativeAssociative ArraysArrays

y each ID key is associated with a value.

y $ages = array("Peter"=>32, "Quagmire"=>30,"Joe"=>34);

y


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MultidimensionalMultidimensional ArraysArrays

y $families = array

("Griffin"=>array ( "Peter", "Lois","Megan" ),

"Quagmire"=>array ( "Glenn" ),

"Brown"=>array ("Cleveland", "Loretta", "Junior"));

y echo "Is " . $families['Griffin'][2] .

" a part of the Griffin family?";y Output=Is Megan a part of the Griffin family?


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PHPPHP FunctionsFunctionsy function functionName()

{code to be executed;}

y


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AddingAdding parametersparameters

y


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y


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PHP FunctionsPHP Functions -- ReturnReturn valuesvalues

y


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PHPPHP Forms and UserForms and User InputInputy

Name: Age:

y When a user fills out the form above and click on the submit button, theform data is sent to a PHP file, called "welcome.php":

y

Welcome !
You are years old.


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PHPPHP $_GET$_GET FunctionFunctiony The built-in $_GET function is used to collect values from

a form sent with method="get".

y Information sent from a form with the GET method isvisible to everyone (it will be displayed in the browser'saddress bar) and has limits on the amount of informationto send.

y Whentousemethod="get"?

y When using method="get" in HTML forms, all variablenames and values are displayed in the URL.

y Note: This method should not be used when sendingpasswords or other sensitive information!

y However, because the variables are displayed in the URL, itis possible to bookmark the page. This can be useful insome cases.

y Note: The get method is not suitable for very largevariable values.


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PHPPHP $_POST$_POST FunctionFunction

y The built-in $_POST function is used to collect valuesfrom a form sent with method="post".

y Information sent from a form with the POST method

is invisible to others and has no limits on the amountof information to send.

y Name: Age:

y Welcome !
You are years old.


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When to use method="post"?When to use method="post"?

y Information sent from a form with the

POST method is invisible to others and

has no limits on the amount of

information to send.y However, because the variables are not

displayed in the URL, it is not possible to

bookmark the page.


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PHP Date FunctionPHP Date Function

date(format,timestamp)

y format - Always required. Specifies the format ofthe timestamp

y timestamp - Optional. Specify UNIX time stamp.

If not passed, the current timestamp is used.

Here are some characters that can be used:

y d - Represents the day of the month (01 to 31)

y m - Represents a month (01 to 12)

y Y - Represents a year (in four digits)


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2010/12/20

2010.12.202010-12-20


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Whatis a cookie?Whatis a cookie?

y A cookie is often used to store data

which can be used to identify a user, for

example, person's username.

y Cookie is a small flat file which sits onusers computer. Each time that user

requests a page or goes to a webpage, all

cookie information is sent too. This isused to identify who you are.


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How to Create a Cookie?How to Create a Cookie?y The setcookie() function is used to set a cookie.

y Note: The setcookie() function must appear BEFORE the tag.

Syntax: setcookie(name,value,expire,path,domain);

y $name - name of the cookie. Example: "username"

y $value - value of the cookie. Example: "john"

y $expire - time (in UNIX timestamp) when the cookie will expire. Example:time()+"3600". Cookie is set to expire after one hour.

y $path - path on the server where cookie will be available.For example, if the path is set to "/", the cookie will be available through out thewhole site. If the cookie is set to say "/news/", the cookie will only be availableunder /news/ and all its sub-directories.

If no path is given, cookie in created under the current directory.

y $domain - domain where cookie will be available. Instead of path you can use

domain settings.For example, if the domian is set to ".yourdomian.com", the cookie will beavailable within the domain nd all its sub-domains, examplenews.yourdomain.com.

If the cookie is set say "www.yourdomian.com" the cookie will be available underall www sub-domains, example " www.yourdomian.com/news


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y The PHP $_COOKIE variable is used to retrieve a

cookie value.y

y Will print john


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print the entire $_COOKIE arrayprint the entire $_COOKIE array

Array ( [username] => john )


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Deleting a Cookie:Deleting a Cookie:


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PHP SessionsPHP Sessions

y Sessions are used to store information which can be usedthrough-out the application for the entire time the user islogged in or running the application. Each time a user visitsyour website, you can create a session for that user to storeinformation pertaining to that user.

y Unlike other applications, in web applications, all the storedvariables and objects are not globally available throughout allpages (unless sent through POST or GET methods to the nextpage), so to tackle this problem sessions are utilized.

y A usage of sessions would be for example, storing products in

a shopping cart. On your favorite merchant site, when you, theuser, clicks on "add to shopping cart", the product informationis then stored in a session (using session variables) which isthen available on the server for later use for the entire thetime you browse the website.


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y When you start a session a unique session id

(PHPSESSID) for each visitor/user is created. Youcan access the session id using the PHP predefinedconstant PHPSESSID.

y The code above starts a session for the user on theserver, and assign a session id for that user'ssession.


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Storinginformationin a sessionStoringinformationin a session

Retrievingstoredsessioninformation


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Destroying/deletingsessioninformationDestroying/deletingsessioninformation

Remember sessions are destroyed automatically

after user leaves your website or closes the

browser, but if you wish to clear a session variable

yourself, you can simple use the unset() functionto clean the session variable.

destroy all session

variables in one go,


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DifferenceDifference betweenSession and CookiebetweenSession and Cookiey If you set the variable to "cookies", then your users will not

have to log in each time they enter your community.

y The cookie will stay in place within the users browser until it isdeleted by the user.

y But Sessions are popularly used, as there is a chance of yourcookies getting blocked if the user browser security setting is sethigh.

y If you set the variable to "sessions", then user activity will betracked using browser sessions, and your users will have to log ineach time they re-open their browser. Additionally, if you areusing the "sessions" variable, you need to secure the "sessions"directory, either by placing it above the web root or by

requesting that your web host make it a non-browsabledirectory.

y The Key difference would be cookies are stored in your harddisk whereas a session aren't stored in your hard disk. Sessionsare basically like tokens, which are generated at authentication. Asession is available as long as the browser is opened.


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PHP:MultidimensionalArraysPHP:MultidimensionalArrays

Title Price Numberrose 1.25 15

Daisy 0.75 25

Orchid 1.15 7


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ThreeThree--dimensionalArraysdimensionalArraysEach element can be referenced by its layer, row,

and column.


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PHPPHP implode()implode() FunctionFunction

implode(separator,array), returns a string

from the elements of an array.


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PHPPHP explode()explode() FunctionFunction

explode(separator,string,limit), breaks a stringinto an array.


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PHPPHP File HandlingFile Handling

howtocreate a file?$ourFileName = "testFile.txt";

$fileptr = fopen($ourFileName, 'w') or

exit("Unable to open file!");fclose($fileptr);


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The file opening modes:The file opening modes:y Modes Description

y r Read only. Starts at the beginning of the file

y r+ Read/Write. Starts at the beginning of the file

y w Write only. Opens and clears the contents of file; orcreates a new file if it doesn't exist

y w+ Read/Write. Opens and clears the contents of file; or

creates a new file if it doesn't existy a Append. Opens and writes to the end of the file or

creates a new file if it doesn't exist

y a+ Read/Append. Preserves file content by writing to the endof the file

y

x Write only. Creates a new file. Returns FALSE and anerror if file already exists

y x+ Read/Write. Creates a new file. Returns FALSE and anerror if file already exists


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y The feof() function checks if the "end-of-file"

(EOF) has been reached. Syntax: feof(file)

y The fgets() function is used to read a single line

from a file. Syntax : fgets(file,length), length is in

bytes.y The fgetc() function is used to read a single

character from a file. Syntax: fgetc(file)

y

The file_exists() function checks whether or nota file or directory exists.

y The filesize() function returns the size of the

specified file.


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y The fread() reads from an open file.

fread(file,length)

y The fseek() function seeks in an open file.fseek(file,offset,whence)

y SEEK_SET - Set position equal to offset. Default

y SEEK_CUR - Set position to current locationplus offset

y SEEK_END - Set position to EOF plus offset

y The ftell() function returns the current positionin an open file

y exit(),and die():Terminates execution of the

script


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y The fwrite() writes to an open file.

y The function will stop at the end of the file or

when it reaches the specified length, whichevercomes first.

y This function returns the number of bytes

written, or FALSE on failure.y fwrite(file,string,length)

y The fputs() writes to an open file.

y fputs(file,string,length)


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PhpPhp file creationfile creation


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Read the fileRead the file

$myFile = "testFile.txt";

$fh = fopen($myFile, 'r');

$theData = fread($fh, filesize($myFile));

fclose($fh);

echo $theData;


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Append data inAppend data in phpphp

$myFile = "testFile.txt";

$fh = fopen($myFile, 'a') or die("can't open file");

$stringData = "New Stuff 1\n"; fwrite($fh,

$stringData);

$stringData = "New Stuff 2\n"; fwrite($fh,

$stringData);

fclose($fh);


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lecture 3 PHP