Lecture3 php by okello erick

IT3101
Web-based Database
Development
Introduction PHP
Dynamic Web Design

An Introduction To PHP
 PHP set its roots in 1995, when an independent
software development contractor named Rasmus
Lerdorf developed a Perl/CGI script that enabled
him to know how many visitors were reading his
online resume.
 Lerdorf thus began giving away his toolset, called
Personal Home Page (PHP), or Hypertext
Preprocessor.
2

 PHP is an embedded server-side Web-scripting
language that provides developers with the
capability to quickly and efficiently build dynamic
Web applications.
 PHP can also serve as a valuable tool for creating
and managing dynamic content, embedded
directly beside JavaScript, Stylesheets and many
others.
 PHP talk to various database systems, giving you
the ability to generate a web page based on a
SQL query.
3

 PHP provides hundreds of predefined
functions and capable of handling anything a
developer can dream of.
Graphic creation and manipulation
Mathematical calculations
Ecommerce
Extensible Markup Language (XML)
Open database connectivity (ODBC)
Macromedia Shockwave.
4

PHP: Hypertext Preprocessor
 PHP is a scripting language that brings websites
to life in the following ways:
 Sending feedback from your website directly to your
mailbox
 Sending email with attachments
 Uploading files to a web page
 Watermarking images
 Generating thumbnails from larger images
 Displaying and updating information dynamically
 Using a database to display and store information
 Making websites searchable
 And much more . .
5

Processing PHP
 PHP is a server-side language. This means that
the web server(apache or IIS) processes your
PHP code and sends only the results usually as
XHTML to the browser.
 Because all the action is on the server, you need
to tell it that your pages contain PHP code. This
involves two simple steps, namely:
 Give every page a PHP filename extension the
default is .php.
 Enclose all PHP code within PHP tags
6

PHP
 HTML and PHP can be used interchangeably as
needed, working alongside one another in
harmony. With PHP, we can simply do the
following:
<html>
<title><?php print "Hello world!"; ?></title>
</html>
 Hello world! will be displayed in the Web page
title bar. Interestingly, the single line print is
enclosed in PHP's escape characters (<?… ?>)
is a complete program.
7

Running PHP
Working with php files
 Create a folder called test in www
 Create a file index.php
 Open a browser, type localhost/test
Note: wamp server must be started and running
8

Index.php
<html>
<title><?php print "Hello world!"; ?></title>
<body>
<?php echo “Welcome to PHP programming"; ?>
</body>
</html>
9

Display of HTML using PHP
<html>
<body>
<?
// Notice how HTML tags are included in the print
statement.
echo "<h3>PHP/HTML integration is cool.</h3>";
?>
</body>
</html>
10

Dynamic date insertion
<? echo date("F d, Y"); ?>
<?php echo date(‘H:i:s’);?>
11

Format Codes for date
12
Code Description
a Lowercase am or pm
A Uppercase AM or PM
d Two-digit day of month, 01–31
D Three-letter day name, Mon–Sun
F Full month name, January–December
g 12-hour hour with no leading zero
G 24-hour hour with no leading zero
h 12-hour hour with leading zero, 01–12
H 24-hour hour with leading zero, 00–23
l Minutes with leading zero, 00–59
j Day of month with no leading zero, 1–31

Format Codes for date
13
Code Description
m Month number with leading zeros, 01–12
l Full day name, Monday–Sunday
M Three letter month name, Jan–Dec
n Month number with no leading zeros, 1–12
s Seconds with leading zero, 00–59
S Ordinal suffix for day of month, st, nd, rd, or th
w Number of day of week, 0–6, where 0 is Sunday
W Week number, 0–53
y Two-digit year number
Y Four-digit year number
z Day of year, 0–365

Comments
 // or # Single-line comment. Everything
to the end of the current line is ignored.
 /* ... */ Single- or multiple-line comment.
Every thing between /* and */ is ignored.
14

The big picture
 A typical PHP page will use some or all of the
following elements:
 Variables to act as placeholders for
unknown or changing values
 Arrays to hold multiple values
 Conditional statements to make decisions
 Loops to perform repetitive tasks
 Functions to perform preset tasks
15

Variables
 A variable is simply a name that you give to
something that may change or that you don’t
know in advance.
 A variable always begins with a dollar sign ($).
The following are all valid variables:
$color
$operating_system
$_some_variable
$model
16

Naming variables
 You can choose just about anything you like as
the name for a variable, as long as you keep the
following rules in mind:
 Variables always begin with a dollar sign ($).
 The first character after the dollar sign cannot be a
number.
 No spaces or punctuation are allowed, except for the
underscore (_).
 Variable names are case-sensitive: $startYear and
$startyear are not the same.
17

Variables
 $sentence = "This is a sentence."; // $sentence
evaluates to string.
 $price = 42.99; // $price evaluates to a floating-
point
 $weight = 185; // $weight evaluates to an integer.
 You can declare variables anywhere in a PHP
script. However, the location of the declaration
greatly influences the realm in which a variable
can be accessed. This access domain is known
as its scope.
18

Variable Scope
 Scope can be defined as the range of
availability a variable has to the program in
which it is declared. PHP variables can be one
of four scope types:
 Local variables
 Function parameters
 Global variables
 Static variables
19

Local Variables
 A variable declared in a function is considered
local; that is, it can be referenced solely in that
function. Any assignment outside of that function
will be considered to be an entirely different
variable from the one contained in the function.
$x = 4;
function assignx () {
$x = 0;
print "$x inside function is $x. <br>";
}
20

Function Parameters
 As is the case with many other programming
languages, in PHP any function that accepts
arguments must declare these arguments in
the function header.
// multiply a value by 10 and return it to the caller
function x10 ($value) {
$value = $value * 10;
return $value;
}
21

Global Variables
 In contrast to local variables, a global variable can
be accessed in any part of the program. However,
in order to be modified, a global variable must be
explicitly declared to be global in the function in
which it is to be modified.
$somevar = 15;
function addit() {
GLOBAL $somevar;
$somevar++;
print "Somevar is $somevar";
}
addit();
22

Static Variables
 In contrast to the variables declared as function
parameters, which are destroyed on the function's
exit, a static variable will not lose its value when
the function exits and will still hold that value
should the function be called again.
 You can declare a variable to be static simply by
placing the keyword STATIC in front of the
variable name.
 STATIC $somevar;
23

String Assignments
 Strings can be delimited in two ways, using either
double quotations ("") or single quotations ('').
 The following two string declarations produce the
same result:
 $food = "meatloaf";
 $food = 'meatloaf';
 However, the following two declarations result in
two drastically different outcomes:
 $sentence = "My favourite food is $food";
 $sentence2 = 'My favourite food is $food';
24

String Assignments
 The following string is what exactly will be
assigned to $sentence. Notice how the variable
$food is automatically interpreted:
My favourite food is meatloaf.
 Whereas $sentence2 will be assigned the string
as follows:
My favourite food is $food.
 These differing outcomes are due to the usage of double and single
quotation marks in assigning the corresponding strings to $sentence and
$sentence2.
25

Supported String Delimiters
SEQUENCE REPRESENTATION
n Newline
r Carriage return
t Horizontal tab
Backslash
$ Dollar sign
" Double-quotation mark
26

Use of String Delimiters
 Double-quoted string recognizes all
available delimiters, a single-quoted string
recognizes only the delimiters "" and "".
 Consider an example of the contrasting
outcomes when assigning strings enclosed
in double and single quotation marks:
$double_list = "item1nitem2nitem3";
$single_list = 'item1nitem2nitem3';
27

Out put
 If you print both strings to the browser, the
double-quoted string will conceal the newline
character, but the single-quoted string will print it
just as if it were any other character.
 Although many of the delimited characters will
be irrelevant in the browser, this will prove to be
a major factor when formatting for various other
media.
 Keep this difference in mind when using double-
or single-quoted enclosures so as to ensure the
intended outcome.
28

Arrays
 An array is a list of elements each having
the same type.
 There are two types of arrays:
a) those that are accessed in accordance with
the index position in which the element
resides
b) those that are associative in nature, accessed
by a key value that bears some sort of
association with its corresponding value.
29

Single-Dimension Arrays
 The general syntax of a single-dimension array is:
$name[index1];
 A single-dimension array can be created as
follows:
$meat[0] = "chicken";
$meat[1] = "steak";
$meat[2] = "turkey";
 If you execute this command:
print $meat[1];
 The following will be output to the browser:
steak
30

 Alternatively, arrays may be created using PHP's
array() function. You can use this function to
create the same $meat array as the one in the
preceding example:
$meat = array("chicken", "steak", "turkey");
 Executing the same print command yields the
same results as in the previous example, again
producing "steak".
31

 You can also assign values to the end of the array
simply by assigning values to an array variable
using empty brackets.
 Therefore, another way to assign values to the
$meat array is as follows:
$meat[] = "chicken";
$meat[] = "steak";
$meat[] = "turkey";
32

Single-Dimension Associative
Arrays
 Associative arrays are particularly convenient
when it makes more sense to map an array using
words rather than integers.
$pairings["zinfandel"] = "Broiled Veal Chops";
$pairings["merlot"] = "Baked Ham";
$pairings["sauvignon"] = "Prime Rib";
$pairings["sauternes"] = "Roasted Salmon";
33

Single-Dimension Associative
Arrays
 An alternative method in which to create an array
is via PHP's array() function:
$pairings = array(
zinfandel => "Broiled Veal Chops",
merlot => "Baked Ham",
sauvignon => "Prime Rib",
sauternes => "Roasted Salmon";
);
 This assignment method bears no difference in
functionality from the previous, other than the format
in which it was created.
34

Multidimensional Indexed Arrays
 Multidimensional indexed arrays function much
like their single-dimension counterparts, except
that more than one index array is used to specify
an element.
 There is no limit as to the dimension size. The
general syntax of a multidimensional array is:
$name[index1] [index2]..[indexN];
 An element of a two-dimensional indexed array
could be referenced as follows:
$position = $chess_board[5][4];
35

PHP's Operators
OPERATOR PURPOSE
++ — Autoincrement, autodecrement
/ * % Division, multiplication, modulus
+ − . Addition, subtraction, concatenation
< <= Less than, less than or equal to,
> >= Greater than, greater than or equal to
== != Is equal to, is not equal to
=== <> identical to, is not equal to
&& || Boolean AND, boolean OR
36

Assignment Operators
EXAMPLE OUTCOME
$a = 5; $a equals 5
$a += 5; $a equals $a plus 5
$a *= 5; $a equals $a multiplied by 5
$a /= 5; $a equals $a divided by 5
$a .= 5; $a equals $a concatenated with 5
37

ASSIGNMENT
 Create a php file that display numbers
from 1-50 on a new line using arrays and
loops. (while/do while)
 Output
1
2
3
4
5
38

Lecture3 php by okello erick

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