UFCE8V-20-3 - PowerPoint Presentation

Slide1

UFCE8V-20-3 Information Systems Development 3

PHP (2) : Functions, User Defined Functions & Environment VariablesSlide2

last lecture …PHP origins & use

Basic Web 1.0 2-tier/3-tier architecture with PHP

PHP as a scripting language (supporting procedural & oo paradigms)

Basic structure & use (statements, variables, control structures, operators)

PHP data types - 5 basic – integer, floating-point, string,

boolean & NULL & 3 complex - array, hash & object

the

exit()

&

die()

statements Slide3

PHP Functions (1) :inbuilt function library (700+)

Basic tasksString 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

Spell-checking Image creation XML

etc.etc.Slide4

PHP Functions (2) :some commonly used built-in functions

FunctionPurposeExampleecho()prints text

echo "Hello World"

;explode()

returns a string as an array split on the specified delimiter

$pizza = "piece1 piece2 piece3

";$pieces

=

explode

(

" "

,

$pizza

);

echo

$pieces

[

1

];

// piece

2

implode()

opposite of explode – joins all the elements of an array using the specified

delimiter

$array

= array(

'

lastname

'

,

'email'

,

'phone'

);

$

comma_separated

=

implode

(

","

,

$array

);

//prints

lastname,email,phone

echo

$

comma_separated

;

isset

()

returns TRUE if a variable exists or FALSE if not

isset

(

$a

);

fopen

()

opens a file for reading (“r” ) or (“w”) writing. Use in conjunction with

fclose

.

$filename

=

"

myfile.txt

"

;

$handle

=

fopen

(

$filename

,

"

r

"

);

$contents

=

fread

($handle

,

filesize

($filename

));

fclose

(

$

ini_handle

);Slide5

PHP Functions

(3) : user defined functions

Declaring a function - functions are declared using the function statement, a name and parenthesis ()

e.g function

myfunction() {…..} - functions can accept any number of arguments and these are separated by

commas inside the parenthesis e.g

function myFunction(arg1, arg2) {…..} - the following simple function prints out any text passed to it as bold

<?

php

function

printBold

($text){

print("<b>$text</b>");

}

print("This Line is not Bold<br>\n"); printBold("This Line is Bold"); print("<br>\n"); print("This Line is not Bold<br>\n"); ?>

r

un exampleSlide6

the return statement - at some point the function will finish and is ready to return control to the caller

- execution then picks up directly after the point the function was called - it is possible to have multiple return points from a function (but this will reduce code readability) - if a return statement includes an expression, return(expression), the value of the expression will be passed back - example:

<?php function makeBold

($text){ $text = "<b>$text</b>"; return($text); }

print("This Line is not Bold<br>\n"); print(makeBold("This Line is Bold") . "<

br>\n"); print("This Line is not Bold<br>\n");

?>

PHP Functions

(4)

: user defined functions

r

un exampleSlide7

- values and references

- for most data types, return values are passed by value - for objects, return values are returned by

reference - the following function creates a

new array of 10 random numbers between 1 and 100 and passes it back as a reference <?php

function &getRandArray() {

$a = array(); for($

i=0; $i<10; $

i

++) {

$a[] = rand(1,100);

}

return($a);

}

$

myNewArray

= &getRandArray(); print_r($myNewArray);

?>

PHP Functions

(5)

: user defined functions

run exampleSlide8

- scope (1) - scoping is way of avoiding clashes between variables in different functions - each code block belongs to a certain scope

- variables within functions have local scope and are private to the function - variables outside a function have a global scope<?php

$a = 1; /* global scope */ function test(){ echo $a; /* reference to local scope variable */

} test();?>The above example will output nothing because the $a inside the function has local scope

PHP Functions

(6) : user defined functionsSlide9

- the global keyword can be used to access variables from the global scope within functions

<?php $a = 1; $b = 2; function Sum(){ global $a, $b;

$b = $a + $b; } Sum(); echo $b;

?> - The above script will output 3. By declaring $a and $b global within the function, all references to either variable will refer to the global version. There is no limit to the number of global variables that can be manipulated by a function.

PHP Functions (7)

: user defined functionsrun exampleSlide10

- arguments - functions expect arguments to to be preceded by a dollar sign ($) and these are usually passed to the function as values

- if an argument has a & sign in front - it is treated as a reference

- the following example shows an argument passed as reference <?php

function stripCommas(&$text){ $text =

str_replace(",", "", $text); } $myNumber

= "10,000"; stripCommas($myNumber);

print($myNumber); ?>

PHP Functions

(8)

: user defined functions

run exampleSlide11

default values - a function can use a default value in an argument using the = sign to precede the argument

- consider the following example <?php function

setName($FirstName = "John", $LastName = "Smith"){

return "Hello, $FirstName $LastName!\n";

} ?>- So, to greet someone called John Smith, you could just use this:

setName();-

To greet someone called Tom Davies, you would use this: setName("Tom", "Davies");

-

To greet someone called Tom Smith, you would use this:

setName

("Tom");

PHP Functions

(9)

: user defined functionsSlide12

Environment & other predefined variables (1)PHP provides a large number of predefined variables to all scripts.

These variables represent everything from external variables to built-in environment variables, last error messages to last retrieved headers.$GLOBALS — References all variables available in global scope

$_SERVER — Server and execution environment information$_GET — HTTP GET variables$_POST — HTTP POST variables$_FILES — HTTP File Upload variables

$_REQUEST — HTTP Request variables$_SESSION — Session variables$_ENV — Environment variables

$_COOKIE — HTTP Cookies$php_errormsg — The previous error message$HTTP_RAW_POST_DATA — Raw POST data

$http_response_header — HTTP response headers$argc — The number of arguments passed to script$

argv — Array of arguments passed to scriptSlide13

Some predefined variables are available to every script in every scope (both local and global) and these are referred to as Superglobals.

For these, there is no need to do global $variable; to access them within functions or methods.The superglobals are:

Environment & other predefined variables (2)

$GLOBALS$_SERVER

$_GET$_POST$_FILES$_COOKIE

$_SESSION$_REQUEST$_ENVSlide14

Environment & other predefined variables (3):the $_REQUEST, $_GET & $_POST

globalsThe most commonly used global variables are $_GET and $_POST which are used to send data from the browser to the server.

$_GET is an associative array (hash) that passes values to the current script using URL parameters. - although the HTTP protocol does not set a limit to how long URL’s can be – different browsers do – so it is considered good practice not to send data that is more than 2000 characters with $_GET

- because the values of $_GET can be read in the URL – no data containing sensitive information (like passwords) should be sent using $_GET - $_GET can't be used to send binary data, like images or word documents,

just textual data.Slide15

Environment & other predefined variables (4):

$_GET example

<?

php

if(

isset

($_GET["name"]) ||

isset

($_GET["age"])) {

echo "<p>Welcome ". $_GET['name']. "<

br

/>";

echo "You are ". $_GET['age']. " years old.</p>";

exit();

}

?>

<html>

<body>

<form action="<?

php

$_PHP_SELF

?>" method="GET">

Name: <input type="text" name="name" />

Age: <input type="text" name="age" />

<input type="submit" />

</form>

</body>

</html>

checks if either the ‘name’ or ‘age’

params. have values set

html form with 3 inputs

f

orm method set to ‘GET’

$

PHP_SELF returns path and name of current script

** Notice that once the form fields are filled in with values of say ‘Popeye’ and ‘83’, the URL shows as http://host/path/function_example_6.php?name=Popeye&age=83 i.e. the parameters are now part of the URL.

v

iew script run scriptSlide16

The POST method transfers information via HTTP headers. - the POST method does not have any restriction on data size to be sent. - it can be used to send ASCII as well as binary data. - the data sent by POST method goes through HTTP header so

security depends on HTTP protocol. By using Secure HTTP (HTTPS) the data can be secured (to a certain extent). - PHP provides the $_POST associative array to access all the sent data using the POST method.

** Note that the example used in the previous slide can be easily changed to make use of the POST method by simply changing the method="GET

" to method=

"POST". The parameters no longer appear in the URL.

$_REQUEST is an associative

array (hash) that by default contains all of the contents of $_GET, $_POST and $_COOKIE

together. ($_COOKIE

superglobal

will

be discussed when we consider PHP sessions).

Environment & other predefined variables (5):

$_POST & $_REQUEST

v

iew script

run script