IT – som værktøj
Bent Thomsen
Institut for Datalogi
Aalborg Universitet
Oktober 2002
Bent Thomsen - FIT 1-1
1
Introduction to PHP
Bent Thomsen
What is PHP?
• PHP is a generalized Open Source Server Side
Scripting Language that generates HTML content
• PHP: Recursive Acronym for
– PHP: Hypertext Preprocessor
• PHP was created by Rasmus Lerdorf in 1994 as a
tool for Web Development
• PHP is simple for beginners, yet a powerful tool
for the professional Web Developer
Embedding PHP in HTML is different from writing a
script in other languages like Perl, but similar to
JavaScript
Instead of writing a program with lots of commands to
output HTML, you write an HTML script with some
embedded code to do something (in the example on the
next page, to output some text).
The PHP code is enclosed in start and end tags that
allow you to jump into and out of "PHP mode".
An example follows
Embedding PHP in HTML
<html>
<head>
<title>Example</title>
</head>
<body>
<?php echo
“Hello World!"; ?>
</body>
</html>
HTML Embedding
– SGML Style: <? echo “Hello World!”; ?>
– XML Style: <?php echo “Hello World!”; ?>
– ASP Style: <%= “Hello World!”; %>
– JavaScript Style:
<script language=“php”>echo “Hello World!”;</script>
PHP vs. JavaScript
• What distinguishes PHP from client-side
JavaScript?
• PHP code is executed on the server.
• If you were to have a script similar to the
above on your server, the client would
receive the results of running that script,
with no way to determine what the
underlying code may be.
Client-side execution using JavaScript
Web-Server
JavaScript
Web-Client
Web-Browser
WWW
HTML Page
...
<SCRIPT ...>
...
Server-side execution using PHP Script
Web-Client
HTML-Form
Call PHP
interpreter
Submit
Form Data
Web-Browser
WWW
Response
Reply
Web-Server
PHP
Script
Response
PHP & Web Servers
PHP supports most web servers including
•Apache
•Microsoft Internet Information Server
• Personal Web Server
•Netscape and iPlanet servers
•Oreilly Website Pro server
•Caudium, Xitami, OmniHTTPd
For most servers PHP has a module, for the
others supporting the CGI standard, PHP can
work as a CGI processor.
PHP VARIABLES
•
•
•
•
•
•
PHP keeps variables easy to work with
Syntax is minimal
All PHP variables start with $
Variable names are case sensitive
Strings, integers, floating-point, arrays
Variables generally come from 3 places
– Assigned within a script
– Passed from an HTML page
– Or from the PHP environment
PHP VARIABLES
• PHP does not require explicit variable
declarations
• Use a variable, and it exists!
• Examples of variable declaration in PHP
–
–
–
–
$a = “this is a string”; //this is a string
$b = 4; //this is an integer
$c = 3.1415; //this is a floating point number
$d = “5”; //this is another string
PHP Is Flexible
• $g = $b + $d ; echo $g will print 9
(See Preceding Slide)
$m = 7; // $m is an integer
$n = 1.732; // $n is double floating point
$p = $m + $n; //$p is also a double floating
point variable
The = sign
• Use = to indicate an assignment statement:
– $X = 4;
• Use = = for comparison:
– If($X==4);
More on Strings
• $my_name = “Wendel”;
• $statement = “Hello, my name is $my_name”;
– This expands the variable $my_name
• So the Echo $statement;
Will print, “Hello, my name is Wendel”
If you want to include any of the following characters in your
string you must first escape each with backslashes “ \ $
Operators
• Assignment (=) – returns a value equal to
the value that was assigned: $a = ($b =
5);
• Arithmetic: + - * \ %
• Concatenation: “now”.“one String”
• Comparison: == != > >= < <=
• Logical: || or xor && and !
Operator Presedence
•
•
•
•
•
•
•
•
•
•
•
(cast)
* \ %
+ < <= >
== !=
&&
||
=
and
xor
or
Can be changed by using
parentheses
>=
e.g.
2*5+6
2*(5+6)
Constants
• You indicate that a label is to represent a constant by:
define(‘CONSTANT_NAME’,value) or
define(‘CONSTANT_NAME’,value,true)
• When the third parameter is present and true then the
parameter label can be used in either upper or lower case
e. g.
define(‘PI’,3.1412,true)
defines a constant PI and another pi that both have the
value 3.1412
Statements
• Function calls: print(“hello”);
• Assignment statements: $first = “first one”;
• If/Then/Else statement:
if (expression){ true_part }
else { false_part }
• While statement:
while (expression)
{ repeated_part }
• For statement:
for (init; test; update)
{ repeated_part }
If/Then/Else
• If/Then/Else statement:
if (expression){ true_part }
else { false_part }
• Used to conditional execute part of a PhP script
• The else part is optional
• Example:
if ($num == 1) { $end = “st”; }
else if ($num == 2 or $num ==3)
{ $end = “ed”; }
else { $end = “th”; }
print (((string)$num).$end);
While
• While statement:
while (expression)
{ repeated_part }
• Loop, that is repeat all the enclosed PhP statements, while
the condition is true
• Example:
$count = 10;
while ($count > 0)
{ print(“the count is $count <br>”);
$count = $count – 1;
}
For
• For statement:
for (init; test; update)
{ repeated_part }
• Execute the init statement, then test the condition; then
repeat the loop
• In the loop, as long as the condition is true, execute the
statements in the body; then execute the update statement;
then test the condition
• Example:
for ($n = 1; $n < 10; $n = $n + 1)
{ print (“the count is $n <br>”);}
Array Examples
• Creating a simple Array
$class = array (“Web Programming II”, “CS463”, “MWF”);
• Creating an Associative Array
$ranks (
“first” =>1,
“second” =>2,
“third” =>3 );
• Heterogeneous Array
$studentA = array ( “StudentA”, “Sr”, 3.4, 103);
• Printing
echo class[2]; // echo out the second element: prints “CS463”;
echo ranks[3]; // echo out the third element: prints 3;
echo studentA[4]; // echo out the cumulative credits: prints 103;
Array - multidimensional
• creating
$students = array(
array( “StudentA”, “FR”, 3.0),
array( “StudentB”, “JR”, 2.8),
array( “StudentC”, “SR”, 3.3) );
• Printing
print $student[2][0]; //prints “StudentC”
• More sophisticated?
$students2 = array(
“StudentA” => array( “Year”=>”FR”, “GPA”=>3.0),
“StudentB” => array( “Year”=>”JR”, “GPA”=>2.8),
“StudentC” => array( “Year”=>”SR”, “GPA”=>3.3) );
• Printing
print $students2[“StudentB”][“GPA”]; // prints 2.8
Functions
• Functions denote actions that can be taken (on your behalf)
by php
• Example
print(“This is some text”);
• Functions can be parts of an expression
• Functions have one or more arguments (the part inside the
parentheses)
• The values of the arguments are past to the functions that
do something with them (“side effects”)
• A Function may return a value (example shortly)
More Functions
• Built-in functions:
– print, round, sqrt, cos, rand, …
• Use defined functions
function diff($par1,$par2){
if ($par1 > $par2){
return $par1 - $par2;
} else {
return $par2 - $par1;
}
}
Commenting in PHP
• /* */
• // to the end of the line
An example
<?php
/* First define functions
use them later */
function diff($par1,$par2){
if ($par1 > $par2){
return $par1 - $par2;
} else {
return $par2 - $par1;
}
}
echo “The difference between 5 and 10 is”;
echo diff(5,10);
?>
Form Handling
• A simple form:
<form action="simple_form.php" method="POST">
Your name: <input type=“text” name=“name”><br/>
You age: <input type=“text” name=“age”><br/>
<input type=“submit”/>
</form>
• The form handling code:
Hi <?php echo $name; ?>.
You are <?php echo $age; ?> years old.
Form Handling
• Magic Global Variables, $HTTP_GET_VARS, $_GET,
register_globals configuration
Hi <?php echo $HTTP_GET_VARS[‘name’]; ?>.
You are <?php echo $_GET[‘age’]; ?> years old.
File Access
• Local File Access
– fopen, fread, fwrite, fclose, fputs, freads, feof, much more…
• Remote File Access
– Uses the same functions as local file access
– Uses URL’s to retrieve files, FTP and HTTP supported.
<?php readfile(‘http://www.ActiveState.com/’); ?>
– Can write files to FTP is username and password is sent
• ftp://username:[email protected]/path/filename
Authentication
<?
function authenticate() {
global $PHP_AUTH_USER;
global $PHP_AUTH_PW;
if(!($PHP_AUTH_USER == “user" && $PHP_AUTH_PW == “password“)) {
Header(‘WWW-Authenticate: basic realm=“My Website“’);
Header(‘HTTP/1.0 401 Unauthorized’);
echo(‘Please enter a username and password to proceed.’);
return false;
}
return true;
}
If (!authenticate()) exit;
echo “You have authenticated properly!”;
?>
SQL Databases
• Wide range of SQL database supported
– MySQL, Postgress, MS-SQL, Oracle, Sybase, ODBC, DBM, Informix…
– Native interfaces (MySQL, etc), and abstracted interfaces (ODBC, dba,
PEAR)
– Persistent connections supported
<?php
$conn = mysql_pconnect(“localhost”, “username”, “password);
mysql_select_db(“mydatabase”, $conn);
$res = mysql_query($conn, “SELECT * FROM resources”);
while (($rs = mysql_fetch_array($res))) {
echo(“column1: “.$rs[0].” column2: “.$rs[1].” …<br>\n”);
}
mysql_close();
?>
Putting it all together
Database
Server
Web-Client
Web-Server
HTML-Form
(+JavaScript)
Web-Browser
WWW
Response
Reply
Call PHP
interpreter
Submit
Data
PHP
Script
Response
DBMS
LAN
SQL
commands
Database
Output
What have we covered?
• A bit about IT history
• Operating systems (Unix)
• Some (hopefully) useful applications
– Browsers, IM, text processing (LaTeX)
• Networks and the Internet (HTML)
• Systems for engineering calculations
– MATLAB and Excel
• Database systems
– Excel and Access
• Programming (JavaScript and PHP)
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