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COMP519: Web Programming
Autumn 2011
PHP Basics:
Introduction to PHP
• a PHP file, PHP workings, running PHP.
Basic PHP syntax
Basic PHP syntax
• variables, operators, if...else...and switch, while, do while, and for.
Some useful PHP functions
How to work with
• HTML forms, cookies, files, time and date.
How to create a basic checker for user-entered data
Server-Side Dynamic Web Programming
•^
CGI is one of the most common approaches to server-side programming^
Universal support:
(almost) Every server supports CGI programming. A great deal of ready-to-use
CGI code. Most APIs (Application Programming Interfaces) also allow CGI programming.
^
Choice of languages:
CGI is extremely general, so that programs may be written in nearly any
language. Perl is by far the most popular, with the result that many people think that CGI meansPerl. But C, C++, Ruby, and Python are also used for CGI programming.
^
Drawbacks:
A separate process is run every time the script is requested. A distinction is made
between HTML pages and code.
•^
Other server
- side alternatives try to avoid the drawbacks
•^
Other server
- side alternatives try to avoid the drawbacks
^
Server-Side Includes (SSI):
Code is
embedded
in HTML pages, and evaluated on the server while
the pages are being served. Add dynamically generated content to an existing HTML page, withouthaving to serve the entire page via a CGI program.
^
Active Server Pages (ASP, Microsoft)
: The ASP engine is integrated into the web server so it does
not require an additional process. It allows programmers to mix code within HTML pages instead ofwriting separate programs. (
Drawback
(?) Must be run on a server using Microsoft server software.)
^
Java Servlets (Sun):
As CGI scripts, they are code that creates documents. These must be
compiled as classes which are dynamically loaded by the web server when they are run.
^
Java Server Pages (JSP):
Like ASP, another technology that allows developers to embed Java in
web pages.
What do You Need?
•^
Our server supports PHP
You don't need to do anything special! *
You don't need to compile anything or install any extra tools!
Create some .php files in your web directory - and the server will parse them for you.
- Slightly different rules apply when dealing with an SQL database (as will be explained when we get to that point).
•^
Most servers support PHP
Download PHP for free here:
http://www.php.net/downloads.php
Download PHP for free here:
http://www.php.net/downloads.php
Download MySQL for free here:
http://www.mysql.com/downloads/index.html
Download Apache for free here:
http://httpd.apache.org/download.cgi
(Note: All of this is already present on the CS servers, so you need not do any installation
yourself to utilize PHP on our machines.)
•Loads of information, including help on individual PHP functionsmay be found at
http://uk.php.net/
Help with PHP
Scalars
All variables in PHP start with a
$
sign symbol. A variable's type is determined by the
context in which that variable is used (i.e. there is no strong-typing in PHP
).
\n";
$txt='1234';
echo "$txt
\n";
$a
=
1234;
echo
"$a
\n";
$a
=
-123;
echo
"$a
\n";
$a
=
1.234;
echo
"$a
\
n";
Four scalar types: boolean
true or false integer, float,
echo
"$a
\
n";
$a
=
1.2e3;
echo
"$a
\n";
$a
=
7E-10;
echo
"$a
\n";
echo
'Arnold
once said:
"I'll
be back"',
"
\n";
$beer
=
'Heineken';
echo
"$beer's
taste
is
great
\n";
$str
=
<<
float,^ floating point numbers string^ single quoteddouble quoted
view the output page
Arrays
An array in PHP is actually an ordered map. A map is a type that maps values to keys.
array()
= creates arrays
"bar", 12 => true);echo $arr["foo"]; // barecho $arr[12];
key
= either an integer or a string.
value
= any PHP type.
43, 32, 56, "b" => 12); array(5 => 43, 6 => 32, 7 => 56, "b" => 12);
if^
no key given
(as in example), the
PHP interpreter uses (maximum of the integer indices + 1).
array(5 => 43, 6 => 32, 7 => 56, "b" => 12); ?>
the integer indices + 1). if^
an existing key
, its value will be
overwritten.
1, 12 => 2); foreach
($arr as $key => $value) { echo $key, ‘=>’,
$value);
$arr[] = 56;
// the same as $arr[13] = 56;
$arr["x"] = 42; // adds a new elementunset($arr[5]); // removes the elementunset($arr);
// deletes the whole array
$a = array(1 => 'one', 2 => 'two', 3 => 'three');unset($a[2]);$b = array_values($a);?>
can set values in an array
unset()
removes a
key/value pair
*Find more on arrays
array_values() makes reindexing effect(indexing numerically)
view the output page
Operators
•^
Arithmetic Operators:
•^
Assignment Operators:
•^
Comparison Operators:
•^
Logical Operators:
Example
Is the same as
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
•^
Logical Operators:
•^
String Operators
:^
.^
and
(for string concatenation)
$a = "Hello ";$b = $a. "World!"; // now $b contains "Hello World!"$a = "Hello ";$a .= "World!";
Conditionals: if else
Can execute a set of code depending on a condition
”; if
$d=="Fri"
echo "Have a nice weekend! ";
else
if (
condition
code to be executed if conditionis
true
else code to be executed if conditionis
false
else
echo "Have a nice day! ";
$x=10;if ($x==10){
echo "Hello";echo "Good morning";
} ?>
date() view the output page
is a built-in PHP function
that can be called with manydifferent parameters to return thedate (and/or local time) invarious formatsIn this case we get a three letterstring for the day of the week.
Looping: while and do-while
Can loop depending on a condition
";$i++; }
"; }
} ?> loops through a block of code if, andas long as, a specified condition istrue
view the output page
} while
$i <= 10
?>
loops through a block of code once,and then repeats the loop as longas a special condition is true (sowill always execute at least once)
view the output page
Looping: for and foreach
Can loop depending on a "counter"
"; } ?> loops through a block of code a
\n”; } ?>
loops through a block of code a specified number of times
loops through a block of code for eachelement in an array
$value)
echo $key." = ".$value."\n"; } ?>
view the output page
Variable Scope
The scope of a variable is the context within which it is defined.
The scope is local within functions,and hence the value of $a isundefined in the “echo” statement.
global refers to itsglobalversion.
static does not loseits value.
view the output page
Including Files
The
include()
statement includes and evaluates the specified file.
vars.php test.php
*The scope of variables in “included” files depends on where the “include” file is added! You can use the include_once, require, and require_once statements in similar ways
view the output page
/*
vars.php is
in
the
scope
of
foo()
so
*^
$fruit
is
NOT
available
outside
of
this
*^
scope.
$color
is
because
we
declared
it
*^
as
global.
*/
foo();
//
A
green
apple
echo "A
$color
$fruit";
//
A
green
?>
view the output page
Server Variables
The
$_SERVER
array variable is a reserved variable that contains all server information.
";
echo "Browser: ".
$_SERVER["HTTP_USER_AGENT"]
. "";
echo "User's IP address: ".
$_SERVER["REMOTE_ADDR"]
?> ";echo "All information";foreach ($_SERVER as $key => $value)
echo $key. " = ". $value. ""; }
?> The $_SERVER is a super global variable, i.e. it's available in all scopes of a PHP script.
view the output page
$_SERVER infoon php.net
File Open
The
fopen(
"file_name"
,
"mode"
)
function is used to open files in PHP.
(use with caution
, i.e. check that this is the case,
otherwise you’ll overwrite an existing file).
For
x
if a file exists, this function fails (and
returns 0).
