PHP * An Introduction - Computing Sciences
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COMP 205 - Week 5
Dr. Chunbo Chu
Agenda
1. Brief History of PHP
2. Basics
3. Advanced
Brief History of PHP
PHP (PHP: Hypertext Preprocessor) was created by Rasmus Lerdorf in 1994. It
was initially developed for HTTP usage logging and server-side form
generation in Unix.
PHP 2 (1995) transformed the language into a Server-side embedded scripting
language. Added database support, file uploads, variables, arrays, recursive
functions, conditionals, iteration, regular expressions, etc.
PHP 3 (1998) added support for ODBC data sources, multiple platform support,
email protocols (SNMP,IMAP), and new parser written by Zeev Suraski and
Andi Gutmans .
PHP 4 (2000) became an independent component of the web server for added
efficiency. The parser was renamed the Zend Engine. Many security features
were added.
PHP 5 (2004) adds Zend Engine II with object oriented programming, robust
XML support using the libxml2 library, SOAP extension for interoperability
with Web Services, SQLite has been bundled with PHP
Brief History of PHP
As of July 2007, PHP is used on 20,917,850 domains, 1,224,183 IP addresses.
http://www.php.net/usage.php Source: Netcraft
Why is PHP used?
1. Easy to Use
Code is embedded into HTML. The PHP code is enclosed in special start
and end tags that allow you to jump into and out of "PHP mode".
<html>
<head>
<title>Example</title>
</head>
<body>
<?php
echo "Hi, I'm a PHP script!";
?>
</body>
</html>
How to output using PHP
echo is the common method in outputting data. Since it
is a language construct, echo doesn’t require parenthesis
like print().
Output Text Usage:
Output the value of a PHP variable:
Echo has a shortcut syntax, but it only works with the
“short open tag” configuration enabled on the server.
<?php echo “Hello World”;
World
<?php echo “$hits”; ?>
of hits
<?= $hits ?>
?>
// prints out Hello
// prints out the number
Examples
3.
Other uses with echo
Automatically generate the year on your pages. This will
print out ©2009 UC Riverside.
©<?php echo date(“Y”);
?>
UC Riverside
You will need to escape any quotation marks with a
backslash.
<?php
echo “I said \”She sells sea shells\” ”; ?>
Why is PHP used?
2. Cross Platform
Runs on almost any Web server on several operating systems.
One of the strongest features is the wide range of supported databases
Web Servers: Apache, Microsoft IIS, Caudium, Netscape Enterprise Server
Operating Systems: UNIX (HP-UX,OpenBSD,Solaris,Linux), Mac OSX,
Windows NT/98/2000/XP/2003
Supported Databases: Adabas D, dBase,Empress, FilePro (read-only),
Hyperwave,IBM DB2, Informix, Ingres, InterBase, FrontBase, mSQL, Direct
MS-SQL, MySQL, ODBC, Oracle (OCI7 and OCI8), Ovrimos, PostgreSQL,
SQLite, Solid, Sybase, Velocis,Unix dbm
Why is PHP used?
3. Cost Benefits
PHP is free. Open source code means that the entire PHP community will
contribute towards bug fixes. There are several add-on technologies
(libraries) for PHP that are also free.
PHP
Software
Free
Platform
Free (Linux)
Development Tools
Free
PHP Coder, jEdit
Server-side Script
User-agent (web browser) requests a web page
• User never sees the PHP, only the
output
http request
• Cannot affect the browser or client PC
•
http
response
Server detects PHP code in page, executes
the code, and sends the output to the user
• Web page (with PHP Output) sent to PC
Getting Started
1.
How to escape from HTML and enter PHP mode
PHP parses a file by looking for one of the special tags that
tells it to start interpreting the text as PHP code. The parser then executes all of
the code it finds until it runs into a PHP closing tag.
HTML
PHP CODE
HTML
<?php echo “Hello World”; ?>
Starting tag
Ending tag
Notes
<?php
?>
Preferred method as it allows the use of PHP
with XHTML
<?
?>
Not recommended. Easier to type, but has to
be enabled and may conflict with XML
<script language="php">
?>
Always available, best if used when FrontPage
is the HTML editor
<%
%>
Not recommended. ASP tags support was
added in 3.0.4
Start your Virtual Machine
Getting Started
2.
Simple HTML Page with PHP
The following is a basic example to output text using
PHP.
<html><head>
<title>My First PHP Page</title>
Semicolons are must!
</head>
<body>
<?php
echo "Hello World!";
?>
</body></html>
•Copy the code onto your web server and save it as “hello.php”.
•Notice that the semicolon is used at the end of each line of PHP
code to signify a line break. Like HTML, PHP ignores whitespace
between lines of code. (An HTML equivalent is <BR>)
Variables
All variables in PHP start with a $ sign symbol.
$var_name = value;
<?php
$txt="Hello World!";
$x=16;
?>
PHP: Loosely Typed
A variable does not need to be declared before adding
a value to it.
Do not have to tell PHP which data type the variable is
PHP automatically converts the variable to the correct
data type, depending on its value.
Compared to a strongly typed programming language..
Naming Rules for Variables
A variable name must start with a letter or an
underscore "_"
A variable name can only contain alpha-numeric
characters and underscores (a-z, A-Z, 0-9, and _ )
A variable name should not contain spaces. If a
variable name is more than one word, it should be
separated with an underscore ($my_string), or with
capitalization ($myString)
PHP String Variables
String variables are used for values that contains
characters.
A string can be used directly in a function or it can be
stored in a variable.
Below, the PHP script assigns the text "Hello World" to
a string variable called $txt:
<?php
$txt="Hello World";
echo $txt;
?>
PHP String Variables
The Concatenation Operator
There is only one string operator in PHP.
The concatenation operator (.) is used to put two string
values together.
To concatenate two string variables together, use the
concatenation operator:
<?php
$txt1="Hello World!";
$txt2="What a nice day!";
echo $txt1 . " " . $txt2;
?>
The output: Hello World! What a nice day!
PHP String Variables
The strlen() function is used to return the length of a
string.
<?php
echo strlen("Hello world!");
?>
The output: 12
The length of a string is often used in loops or other
functions, when it is important to know when the
string ends. (i.e. in a loop, we would want to stop the
loop after the last character in the string).
PHP String Variables
The strpos() function is used to search for character within
a string.
If a match is found, this function will return the position of
the first match. If no match is found, it will return FALSE.
<?php
echo strpos("Hello world!","world");
?>
The output: 6
The position of the string "world" in our string is position
6. The reason that it is 6 (and not 7), is that the first
position in the string is 0, and not 1
PHP Operators
Arithmetic Operators
Operator Description
Example
Result
+
Addition
x=2
x+2
4
-
Subtraction
x=2
5-x
3
*
Multiplication
x=4
x*5
20
/
Division
15/5
5/2
3
2.5
%
Modulus (division
remainder)
5%2
10%8
10%2
1
2
0
++
Increment
x=5
x++
x=6
--
Decrement
x=5
x--
x=4
PHP Operators
Assignment 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
PHP Operators
Comparison Operators
Operator Description
==
is equal to
Example
5==8 returns false
!=
>
<
>=
is not equal
is greater than
is less than
is greater than or equal to
5!=8 returns true
5>8 returns false
5<8 returns true
5>=8 returns false
<=
is less than or equal to
5<=8 returns true
PHP Operators
Logical Operators
Operator Description
&&
and
Example
x=6
y=3 (x < 10 && y > 1) returns
true
||
or
x=6
y=3 (x==5 || y==5) returns false
!
not
x=6
y=3 !(x==y) returns true
Conditional Statements
Conditional statements are very useful for displaying specific content
to the user.
The if Statement
Use the if statement to execute some code only if a specified condition is true.
if (condition)
code to be executed if condition is true;
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri") echo "Have a nice weekend!";
?>
</body>
</html>
Conditional Statements
The if...else Statement
if (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
{
echo "Hello!<br />";
echo "Have a nice weekend!";
echo "See you on Monday!";
}
?>
</body>
</html>
<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!";
elseif ($d=="Sun")
echo "Have a nice Sunday!";
else
echo "Have a nice day!";
?>
</body>
</html>
Switch Statement
switch (n)
{
case label1:
code to be executed if n=label1;
Don’t forget break!
break;
case label2:
code to be executed if n=label2;
break;
default:
code to be executed if n is different from both label1
and label2;
}
<html>
<body>
<?php
switch ($x)
{
case 1:
echo "Number 1";
break;
case 2:
echo "Number 2";
break;
case 3:
echo "Number 3";
break;
default:
echo "No number between 1 and 3";
}
?>
</body>
</html>
Array
An array is a special variable, which can hold more
than one value, at a time.
$cars1="Saab";
$cars2="Volvo";
$cars3="BMW";
An array can hold all your variable values under a
single name
Three kinds of arrays:
Numeric array - An array with a numeric index
Associative array - An array where each ID key is associated with a value
Multidimensional array - An array containing one or more arrays
Numeric Arrays
Numeric index
$cars=array("Saab","Volvo","BMW","Toyota");
$cars[0]="Saab";
$cars[1]="Volvo";
$cars[2]="BMW";
$cars[3]="Toyota";
echo $cars[0] . " and " . $cars[1] . " are Swedish cars."
Associative Arrays
When storing data about specific named values, a
numerical array is not always the best way to do it.
Each ID key is associated with a value.
We can use the values as keys and assign values to
them.
$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);
A different way
<?php
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
echo "Peter is " . $ages['Peter'] . " years old.";
?>
Multidimensional Arrays
Each element in the main array can also be an array.
Each element in the sub-array can be an array, and so on.
$families = array
(
"Griffin"=>array
(
"Peter",
"Lois",
"Megan"
),
"Quagmire"=>array
(
"Glenn"
),
"Brown"=>array
(
"Cleveland",
"Loretta",
"Junior"
)
);
echo "Is " . $families['Griffin'][2] .
" a part of the Griffin family?";
The code above will output:
Is Megan a part of the Griffin family?
Looping
The same block of code to run over and over again
Looping statements:
while - loops through a block of code while a specified
condition is true
do...while - loops through a block of code once, and
then repeats the loop as long as a specified condition is
true
for - loops through a block of code a specified number
of times
foreach - loops through a block of code for each
element in an array
while
<html>
<body>
<?php
$i=1;
while($i<=5)
{
echo "The number is " . $i . "<br />";
$i++;
}
?>
</body>
</html>
do...while
<html>
<body>
<?php
$i=1;
do
{
$i++;
echo "The number is " . $i . "<br />";
}
while ($i<=5);
?>
</body>
</html>
for
for (init; condition; increment)
{
code to be executed;
}
Parameters:
init: Mostly used to set a counter (but can be any code to be
executed once at the beginning of the loop)
condition: Evaluated for each loop iteration. If it evaluates to
TRUE, the loop continues. If it evaluates to FALSE, the loop
ends.
increment: Mostly used to increment a counter (but can be
any code to be executed at the end of the loop)
for
<html>
<body>
<?php
for ($i=1; $i<=5; $i++)
{
echo "The number is " . $i . "<br />";
}
?>
</body>
</html>
foreach
<html>
<body>
<?php
$x=array("one","two","three");
foreach ($x as $value)
{
echo $value . "<br />";
}
?>
</body>
</html>
Activity
Implement the following table in a multi-dimensional
array "student“:
Name ID
Tom
0001
Grade
98
John
Jane
81
70
0005
0006
Output the student table in form of a table.
<html>
<body>
<?php
$student=array(
array("Tom","001", "98"),
array("John","002", "81"),
array("Jane", "003", "67")
);
echo "<table border=1> <tr> <th>Name</th> <th>ID</th> <th>Score</th></tr>";
foreach ($student as $person)
{
echo "<tr>";
foreach ($person as $x)
echo "<td>". $x."</td>";
echo "</tr>";
}
echo "</table>";
?>
</body>
Functions
The real power of PHP: more than 700 built-in
functions.
To keep the browser from executing a script when the
page loads, you can put your script into a function.
A function will be executed by a call to the function.
You may call a function from anywhere within a page.
Create a PHP Function
A function will be executed by a call to the function.
function functionName()
{
code to be executed;
}
Adding parameters
<html>
<body>
<?php
function writeName($fname)
{
echo $fname . " Refsnes.<br />";
}
echo "My name is ";
writeName("Kai Jim");
echo "My sister's name is ";
writeName("Hege");
echo "My brother's name is ";
writeName("Stale");
?>
</body>
</html>
Return values
<html>
<body>
<?php
function add($x,$y)
{
$total=$x+$y;
return $total;
}
echo "1 + 16 = " . add(1,16);
?>
</body>
</html>
Activity
Implement the following functions for the student table:
A “grade($score)" function that convert a numeric score
into a letter grade:
$score >=90 A
$score >=80 B
$score >=70 C
$score >=60 D
$score <60 F
Call grade($score) function and output the table with the
letter grade
Forms and User Input
Any form element in an HTML page will
automatically be available to your PHP scripts.
<html>
<body>
<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
</body>
</html>
welcome.php
<html>
<body>
Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
</body>
</html>
•Browser validation is faster and reduces the server load.
•Consider server validation if the user input will be inserted
into a database
$_GET Function
Built-in $_GET function is used to collect values in a
form with method="get".
GET method
Information is visible to everyone (it will be displayed in
the browser's address bar)
Has limits on the amount of information to send (max.
100 characters).
Example
<form action="welcome.php" method="get">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
When the user clicks the "Submit" button, the URL sent to
the server could look something like this:
http://www.w3schools.com/welcome.php?fname=Peter&age=37
The "welcome.php" file can now use the $_GET function to
collect form data (the names of the form fields will
automatically be the keys in the $_GET array):
Welcome <?php echo $_GET["fname"]; ?>.<br />
You are <?php echo $_GET["age"]; ?> years old!
When to use method="get"?
When using method="get" in HTML forms, all variable
names and values are displayed in the URL.
Note: This method should not be used when sending
passwords or other sensitive information!
However, because the variables are displayed in the
URL, it is possible to bookmark the page. This can be
useful in some cases.
Note: The get method is not suitable for large variable
values; the value cannot exceed 100 characters.
$_POST Function
Built-in $_POST function is used to collect values from
a form sent with method="post".
POST method
Information sent from a form is invisible to others
Has no limits on the amount of information to send
Example
<form action="welcome.php" method="post">
Name: <input type="text" name="fname" />
Age: <input type="text" name="age" />
<input type="submit" />
</form>
When the user clicks the "Submit" button, the URL will
look like this:
http://www.w3schools.com/welcome.php
The "welcome.php" file can now use the $_POST function
to collect form data (the names of the form fields will
automatically be the keys in the $_POST array):
Welcome <?php echo $_POST["fname"]; ?>!<br />
You are <?php echo $_POST["age"]; ?> years old.
When to use method="post"?
Information sent from a form with the POST method is
invisible to others and has no limits on the amount of
information to send.
However, because the variables are not displayed in the
URL, it is not possible to bookmark the page.
The PHP $_REQUEST Function
The PHP built-in $_REQUEST function contains the contents
of both $_GET, $_POST, and $_COOKIE.
The $_REQUEST function can be used to collect form data
sent with both the GET and POST methods.
Example
Welcome <?php echo $_REQUEST["fname"]; ?>!<br />
You are <?php echo $_REQUEST["age"]; ?> years old.
Advanced features
Server Side Includes (SSI)
You can insert the content of one PHP file into another PHP file before
the server executes it, with the include() or require() function.
The two functions are identical in every way, except how they handle
errors:
include() generates a warning, but the script will continue execution
require() generates a fatal error, and the script will stop
These two functions are used to create functions, headers, footers, or
elements that will be reused on multiple pages.
Server side includes saves a lot of work. This means that you can create
a standard header, footer, or menu file for all your web pages. When the
header needs to be updated, you can only update the include file, or
when you add a new page to your site, you can simply change the menu
file (instead of updating the links on all your web pages).
Example
To implement templates on your website.
Examples
Step 1: Universal header and footer in a single file
Create a file called header.php. This file will have all of the
header HTML code. You can use Aptana/Dreamweaver to create the
header, but remember to remove the closing </body> and </html> tags.
<html><head>
<title>UCR Webmaster Support Group</title>
<link rel="stylesheet" type="text/css" href=“mycssfile.css">
</head>
<body>
<table width=80% height=30>
<tr><td>
<div align=center> Page Title </div>
</td></tr></table>
Examples
Step 2: Universal header and footer in a single file
Next, create a file called footer.php. This file will have all of the footer
HTML code.
<table width=80% height=30>
<tr><td>
<div align=center> UC Riverside Department<BR>
<a href=mailto:someuser@ucr.edu>someuser@ucr.edu</a>
</div>
</td></tr></table>
</body>
</html>
Examples
Step 3: Universal header and footer in a single file
This is the basic template that you will use on all of the pages. Make sure you name the
files with a .php extension so that the server will process the PHP code. In this
example, we assume the header and footer files are located in the same directory.
<?php
// header
include(“header.php”);
?>
Insert content here!
<?php
// footer
include(“footer.php”);
?>
Examples
Benefits:
- Any changes to header or footer only require editing of a single file. This
reduces the amount of work necessary for site maintenance and
redesign.
- Helps separate the content and design for easier maintenance.
Header
Page 1
Content
Page 2
Content
Page 3
Content
Footer
Page 4
Content
Page 5
Content
File Handling
fopen() function
<html>
<body>
<?php
$file=fopen("welcome.txt","r");
?>
</body>
</html>
Returns 0 (false) if unable to open the specified file.
File open modes
Modes
Description
r
Read only. Starts at the beginning of the file
r+
Read/Write. Starts at the beginning of the file
w
Write only. Opens and clears the contents of file; or
creates a new file if it doesn't exist
w+
Read/Write. Opens and clears the contents of file; or
creates a new file if it doesn't exist
a
Append. Opens and writes to the end of the file or
creates a new file if it doesn't exist
a+
Read/Append. Preserves file content by writing to the
end of the file
x
Write only. Creates a new file. Returns FALSE and an
error if file already exists
x+
Read/Write. Creates a new file. Returns FALSE and an
error if file already exists
Closing a File
<?php
$file = fopen("test.txt","r");
//some code to be executed
fclose($file);
?>
Check End-of-file
if (feof($file)) echo "End of file";
Note: You cannot read from files opened in w, a, and x mode!
Reading a File Line by Line
echo fgets($file);
Reading a File Character by Character
echo fgetc($file);
Examples
To implement a simple page counter
Examples
<?php
$COUNTER_FILE = “webcounter.txt";
if (file_exists($COUNTER_FILE)) {
$fp = fopen("$COUNTER_FILE", "r+");
flock($fp, 1);
$hits = fgets($fp, 4096);
$hits += 1;
fseek($fp,0);
fputs($fp, $hits);
flock($fp, 3);
fclose($fp);
}
?>
Examples
Next, output the counter value using PHP.
Copy this line after the main block of code.
This page has been viewed <?php echo“$hits”; ?> times.
• That’s it! The result should look something similar to:
Examples
You can change the text around the
<?php echo“$hits”; ?> tags to your liking.
<?php echo“$hits”; ?> visitors.
File Upload
Create an Upload-File Form
<html>
<body>
<form action="upload_file.php" method="post"
enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file" />
<br />
<input type="submit" name="submit" value="Submit" />
</form>
</body>
</html>
specifies which contenttype (binary
input
should data).
be processed
as a file.
upload_file.php
<?php
if ($_FILES["file"]["error"] > 0)
{
echo "Error: " . $_FILES["file"]["error"] . "<br
/>";
}
else
{
echo "Upload: " . $_FILES["file"]["name"] . "<br
/>";
echo "Type: " . $_FILES["file"]["type"] . "<br />";
echo "Size: " . ($_FILES["file"]["size"] / 1024) .
" Kb<br />";
echo "Stored in: " . $_FILES["file"]["tmp_name"];
}
?>
Exercise
Write an HTML form and a PHP script that:
Allow user to upload only JPG image files.
Hint: For IE to recognize jpg files the type must be
pjpeg, for FireFox it must be jpeg.
When a JPG is uploaded, display it in the browser.
Cookies
A cookie is often used to identify a user.
A small file that the server embeds on the user's
computer.
Each time the same computer requests a page with a
browser, it will send the cookie too.
With PHP, you can both create and retrieve cookie
values.
To Create a Cookie
setcookie(name, value, expire, path, domain);
<?php
setcookie("user", "Alex Porter", time()+3600);
?>
<html>
....
Note: The setcookie() function must appear BEFORE the
<html> tag.
Retrieve a Cookie Value
The PHP $_COOKIE variable is used to retrieve a cookie value
<html>
<body>
<?php
if (isset($_COOKIE["user"]))
echo "Welcome " . $_COOKIE["user"] . "!<br />";
else
echo "Welcome guest!<br />";
?>
</body>
</html>
How to Delete a Cookie?
When deleting a cookie you should assure that the
expiration date is in the past.
<?php
// set the expiration date to one hour ago
setcookie("user", "", time()-3600);
?>
Sessions
A PHP session allows you to store user information on
the server for later use (i.e. username, shopping items,
etc).
However, session information is temporary and will be
deleted after the user has left the website.
If you need a permanent storage you may want to store
the data in a database.
Sessions work by creating a unique id (UID) for each
visitor and store variables based on this UID. The UID
is either stored in a cookie or is propagated in the URL.
Starting a PHP Session
Before you can store user information in your PHP
session, you must first start up the session.
Note: The session_start() function must appear
BEFORE the <html> tag:
<?php session_start(); ?>
<html>
<body>
</body>
</html>
Storing a Session Variable
The correct way to store and retrieve session variables is to use the PHP
$_SESSION variable:
<?php
session_start();
// store session data
$_SESSION['views']=1;
?>
<html>
<body>
<?php
//retrieve session data
echo "Pageviews=". $_SESSION['views'];
?>
</body>
</html>
The isset() function checks if the "views" variable has
already been set
<?php
session_start();
if(isset($_SESSION['views']))
$_SESSION['views']=$_SESSION['views']+1;
else
$_SESSION['views']=1;
echo "Views=". $_SESSION['views'];
?>
Destroying a Session
The unset() function is used to free the specified
session variable:
<?php
unset($_SESSION['views']);
?>
Completely destroy the session by calling the
session_destroy() function:
<?php
session_destroy();
?>
Additional Resources
PHP Manual http://docs.php.net/
PHP Tutorial http://academ.hvcc.edu/~kantopet/php/index.php
PHP Coder http://www.phpide.de/
JEdit http://www.jedit.org/
PHP's creator offers his thoughts on the PHP phenomenon, what has shaped and
motivated the language, and where the PHP movement is heading
http://www.oracle.com/technology/pub/articles/php_experts/rasmus_php.html
Hotscripts – A large number of PHP scripts can be found at:
http://hotscripts.com/PHP/Scripts_and_Programs/index.html
Additional Information
Some of the new functions added in version 5:
Arrays:
array_combine() - Creates an array by using one array for keys and another for its values
array_walk_recursive() - Apply a user function recursively to every member of an array
Date and Time Related:
idate() - Format a local time/date as integer
date_sunset() - Time of sunset for a given day and location
date_sunrise() - Time of sunrise for a given day and location
time_nanosleep() - Delay for a number of seconds and nano seconds
Strings:
str_split() - Convert a string to an array
strpbrk() - Search a string for any of a set of characters
substr_compare() - Binary safe optionally case insensitive comparison of two strings from an
offset, up to length characters
Other:
php_check_syntax() - Check the syntax of the specified file
php_strip_whitespace() - Return source with stripped comments and whitespace
