Bài giảng Web technologies and e-Services - Bài 2, Phần 3: Introduction to PHP - Nguyễn Bình Minh
11/03/2021
IT4409: Web Technologies and e-Services
2020-2
Introduction to PHP
•Instructor: Dr. Thanh-Chung Dao
•Slides by Dr. Binh Minh Nguyen
Department of Information Systems
School of Information and Communication Technology
Hanoi University of Science and Technology
1
Content
PHP Basics:
§ Introduction to PHP
• a PHP file, PHP workings, running PHP.
§ 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
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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 means
Perl. But C, C++, Ruby, and Python are also used for CGI programming.
§ Drawbacks: Old. 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
§ 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, without
having 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 of
writing 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.
3
PHP
•
developed in 1995 by Rasmus Lerdorf (member of the Apache Group)
§ originally designed as a tool for tracking visitors at Lerdorf's Web site
§ within 2 years, widely used in conjunction with the Apache server
§ developed into full-featured, scripting language for server-side programming
§ free, open-source
§ server plug-ins exist for various servers
§ now fully integrated to work with mySQL databases
•
•
PHP is similar to JavaScript, only it’s a server-side language
§ PHP code is embedded in HTML using tags
§ when a page request arrives, the server recognizes PHP content via the file extension (.php
or .phtml)
§ the server executes the PHP code, substitutes output into the HTML page
§ the resulting page is then downloaded to the client
§ user never sees the PHP code, only the output in the page
The acronym PHP means (in a slightly recursive definition)
§ PHP: Hypertext Preprocessor
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What do You Need?
•
•
Most 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.
Most servers support PHP
5
Help with PHP
•Loads of information, including help on individual PHP functions
may be found at
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Basic PHP syntax
A PHP scripting block always starts with <?phpand ends with ?>. A PHP scripting block
can be placed (almost) anywhere in an HTML document.
<html>
print and echo
for output
<!-- hello.php CS443 -->
<head><title>Hello World</title></head>
<body>
<p>This is going to be ignored by the PHP interpreter.</p>
a semicolon (;)
<?php echo '<p>While this is going to be parsed.</p>'; ?>
at the end of each
<p>This will also be ignored by the PHP preprocessor.</p>
statement
<?php print('<p>Hello and welcome to <i>my</i> page!</p>');
?>
<?php
// for a single-line comment
//This is
a comment
/* and */ for a large
comment block.
/*
This is
a
comment
block
*/
?>
view the output page
</body>
</html>
The server executes the print and echo statements, substitutes output.
7
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).
<html><head></head>
<!-- scalars.php CS443 -->
<body> <p>
<?php
$foo
= true; if ($foo) echo "It is TRUE! <br /> \n";
Four scalar types:
boolean
true or false
integer,
$txt='1234'; echo "$txt <br /> \n";
$a
$a
=
=
1234; echo "$a <br /> \n";
-123;
echo "$a <br /> \n";
$a 1.234;
echo "$a <br /> \n";
$a 1.2e3;
echo "$a <br /> \n";
$a 7E-10;
=
=
float,
floating point numbers
string
=
echo "$a <br /> \n";
echo 'Arnold once said: "I\'ll be back"', "<br /> \n";
$beer
echo "$beer's taste is great <br /> \n";
$str <<<EOD
= 'Heineken';
single quoted
double quoted
=
Example of string
spanning multiple lines
using “heredoc” syntax.
EOD;
echo $str;
?>
</p>
view the output page
</body>
</html>
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Arrays
An array in PHP is actually an ordered map. A map is a type that maps values to keys.
array()= creates arrays
<?php
$arr = array("foo" => "bar", 12 => true);
key = either an integer or a string.
echo $arr["foo"]; // bar
echo $arr[12];
// 1
value = any PHP type.
?>
if no key given (as in example), the
PHP interpreter uses (maximum of
the integer indices + 1).
<?php
array(5 => 43, 32, 56, "b" => 12);
array(5 => 43, 6 => 32, 7 => 56, "b" => 12);
?>
if an existing key, its value will be
overwritten.
<?php
can set values in an array
$arr = array(5 => 1, 12 => 2);
foreach ($arr as $key => $value) { echo $key, '=>',
$value);
// the same as $arr[13] = 56;
$arr["x"] = 42; // adds a new element
unset($arr[5]); // removes the element
}
unset()removes a
$arr[] = 56;
key/value pair
array_values()
makes reindexing effect
(indexing numerically)
unset($arr);
// deletes the whole array
$a = array(1 => 'one', 2 => 'two', 3 => 'three');
unset($a[2]);
$b = array_values($a);
?>
view the output page
*Find more on arrays
9
Constants
A constant is an identifier (name) for a simple value. A constant is case-sensitive by
default. By convention, constant identifiers are always uppercase.
<?php
// Valid constant names
define("FOO",
"something");
define("FOO2",
"something else");
define("FOO_BAR", "something more");
You can access
constants anywhere
in your script
without regard to
scope.
// Invalid constant names (they shouldn’t start
//
with a number!)
define("2FOO",
"something");
// This is valid, but should be avoided:
// PHP may one day provide a "magical" constant
// that will break your script
define("__FOO__", "something");
?>
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Operators
Example
x+=y
Is the same as
x=x+y
• Arithmetic Operators: +, -, *,/ , %, ++, --
x-=y
x*=y
x/=y
x%=y
x=x-y
x=x*y
x=x/y
x=x%y
• Assignment Operators: =, +=, -=, *=, /=, %=
• Comparison Operators: ==, !=, >, <, >=, <=
• Logical Operators: &&, ||, !
• String Operators: . and .= (for string concatenation)
$a = "Hello ";
$b = $a . "World!"; // now $b contains "Hello World!"
$a = "Hello ";
$a .= "World!";
11
Conditionals: if else
Can execute a set of code depending on a condition
<html><head></head>
<!-- if-cond.php CS443 -->
<body>
if (condition)
code to be executed if condition
is true;
<?php
$d=date("D");
echo $d, "<br/>";
else
code to be executed if condition
is false;
if ($d=="Fri")
echo "Have a nice weekend! <br/>";
else
echo "Have a nice day! <br/>";
date() is a built-in PHP function
that can be called with many
different parameters to return the
date (and/or local time) in
various formats
$x=10;
if ($x==10)
{
echo "Hello<br />";
echo "Good morning<br />";
}
In this case we get a three letter
string for the day of the week.
?>
</body>
</html>
view the output page
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Conditionals: switch
Can select one of many sets of lines to execute
<html><head></head>
<body>
<!–- switch-cond.php CS443 -->
<?php
$x = rand(1,5); // random integer
echo "x = $x <br/><br/>";
switch (expression)
{
switch ($x)
{
case 1:
echo "Number 1";
case label1:
code to be executed if
expression = label1;
break;
break;
case label2:
code to be executed if
expression = label2;
break;
default:
code to be executed
if expression is different
case 2:
echo "Number 2";
break;
case 3:
echo "Number 3";
break;
default:
from both label1 and label2;
break;
echo "No number between 1 and 3";
break;
}
}
?>
view the output page
</body>
</html>
13
Looping: while and do-while
Can loop depending on a condition
<html><head></head>
<body>
<html><head></head>
<body>
<?php
<?php
$i=1;
while($i <= 5)
$i=0;
do
{
{
echo "The number is $i <br />";
$i++;
$i++;
echo "The number is $i <br />";
}
?>
}
while($i <= 10);
?>
</body>
</html>
view the output page
</body>
</html>
view the output page
loops through a block of code if, and
as long as, a specified condition is
true
loops through a block of code once,
and then repeats the loop as long
as a special condition is true (so
will always execute at least once)
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Looping: for and foreach
Can loop depending on a "counter"
<?php
<?php
for ($i=1; $i<=5; $i++)
$a_array = array(1, 2, 3, 4);
{
foreach ($a_array as $value)
{
echo "Hello World!<br />";
}
$value = $value * 2;
?>
echo "$value <br/> \n";
}
?>
loops through a block of code a
specified number of times
<?php
$a_array=array("a","b","c");
foreach ($a_array as $key => $value)
{
echo $key . " = " . $value . "\n";
}
?>
view the output page
loops through a block of code for each
element in an array
15
User Defined Functions
Can define a function using syntax such as the following:
<?php
function foo($arg_1, $arg_2, /* ..., */ $arg_n)
{
Can also define conditional
functions, functions within functions,
and recursive functions.
echo "Example function.\n";
return $retval;
}
?>
Can return a value of any type
<?php
<?php
function square($num)
function small_numbers()
{
{
return $num
*
$num;
return array (0, 1, 2);
}
}
echo square(4);
?>
list ($zero, $one, $two) = small_numbers();
echo $zero, $one, $two;
?>
<?php
function takes_array($input)
{
echo "$input[0]
+ $input[1] = ", $input[0]+$input[1];
}
view the output page
takes_array(array(1,2));
?>
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Variable Scope
The scope of a variable is the context within which it is defined.
<?php
$a = 1; /* limited variable scope */
function Test()
{
The scope is local within functions,
echo $a;
/* reference to local scope variable */
and hence the value of $a is
}
undefined in the “echo” statement.
Test();
?>
<?php
$a = 1;
$b = 2;
function Sum()
<?php
function Test()
{
global
static
static $a = 0;
echo $a;
$a++;
{
refers to its
global
version.
does not lose
its value.
global $a, $b;
$b = $a + $b;
}
}
Test1();
Test1();
Test1();
?>
Sum();
echo $b;
?>
view the output page
17
Including Files
The include() statement includes and evaluates the specified file.
// vars.php
<?php
<?php
function foo()
{
$color
$fruit
=
=
'green';
'apple';
global $color;
?>
include ('vars.php‘);
// test.php
<?php
echo "A $color $fruit";
}
echo "A $color $fruit"; //
A
A
/* 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.
*
*
include 'vars.php';
*/
echo "A $color $fruit"; //
green apple
foo();
//
A
green apple
?>
echo "A $color $fruit"; //
A green
?>
view the output page
view the output page
*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.
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PHP Information
The phpinfo()function is used to output PHP information about the version installed
on the server, parameters selected when installed, etc.
<html><head></head>
<!– info.php CS443
<body>
<?php
// Show all PHP information
phpinfo();
?>
INFO_GENERAL
The configuration line,
php.ini location,
build date,
Web Server,
System and more
INFO_CREDITS
INFO_CONFIGURATION Local and master values
PHP 4 credits
<?php
// Show only the general information
phpinfo(INFO_GENERAL);
for php directives
INFO_MODULES
Loaded modules
?>
</body>
</html>
INFO_ENVIRONMENT
Environment variable
information
INFO_VARIABLES
All predefined variables
from EGPCS
view the output page
INFO_LICENSE
PHP license information
INFO_ALL Shows all of the above (default)
19
Server Variables
The $_SERVERarray variable is a reserved variable that contains all server information.
<html><head></head>
<body>
<?php
echo "Referer: " . $_SERVER["HTTP_REFERER"] . "<br />";
echo "Browser: " . $_SERVER["HTTP_USER_AGENT"] . "<br />";
echo "User's IP address: " . $_SERVER["REMOTE_ADDR"];
?>
<?php
echo "<br/><br/><br/>";
echo "<h2>All information</h2>";
foreach ($_SERVER as $key => $value)
$_SERVER info
on php.net
{
echo $key . " = " . $value . "<br/>";
}
?>
view the output page
</body>
</html>
The $_SERVER is a super global variable, i.e. it's available in all scopes of a PHP script.
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File Open
The fopen("file_name","mode")function is used to open files in PHP.
r
Read only.
Write only.
Append.
r+
w+
a+
Read/Write.
Read/Write.
Read/Append.
Create and open for read/write.
w
a
x
Create and open for write only. x+
For w, and a, if no file exists, it tries to create it
(use with caution, i.e. check that this is the case,
otherwise you’ll overwrite an existing file).
<?php
$fh=fopen("welcome.txt","r");
?>
For x if a file exists, this function fails (and
returns 0).
<?php
if
( !($fh=fopen("welcome.txt","r")) )
exit("Unable to open file!");
?>
If the fopen()function is unable to open
the specified file, it returns 0 (false).
21
File Workings
fclose()closes a file.
feof()determines if the end is true.
fgetc()reads a single character
fgets()reads a line of data
fwrite(), fputs ()
writes a string with and without \n
file()reads entire file into an array
<?php
<?php
$myFile = "welcome.txt";
$myFile = "welcome.txt";
if (!($fh=fopen($myFile,'r')))
exit("Unable to open file.");
$fh = fopen($myFile, 'r');
$theData = fgets($fh);
while (!feof($fh))
{
fclose($fh);
echo $theData;
view the output page
$x=fgetc($fh);
?>
echo $x;
}
fclose($fh);
<?php
view the output page
$myFile = "testFile.txt";
?>
$fh = fopen($myFile, 'a') or
die("can't open file");
<?php
$stringData = "New Stuff 1\n";
fwrite($fh, $stringData);
$stringData = "New Stuff 2\n";
fwrite($fh, $stringData);
$lines = file('welcome.txt');
foreach ($lines as $l_num => $line)
{
fclose($fh);
view the output page
?>
.$elcihnoe."”L<ibnre/>#”{;$lv_ineuwm}th:e“output page
}
?>
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Form Handling
Any form element is automatically available via one of the built-in PHP variables (provided
that HTML element has a “name” defined with it).
<html>
<-- form.html CS443 -->
<body>
<form action="welcome.php" method="post">
Enter your name: <input type="text" name="name" /> <br/>
Enter your age: <input type="text" name="age" /> <br/>
<input type="submit" /> <input type="reset" />
</form>
</body>
</html>
<html>
$_POST
<!–- welcome.php COMP 519 -->
<body>
contains all POST data.
Welcome <?php echo $_POST["name"]."."; ?><br />
You are <?php echo $_POST["age"]; ?> years old!
$_GET
contains all GET data.
</body>
</html>
view the output page
23
HTTP Post vs. Get
• GET is used to request data from a specified resource
§ Note that the query string (name/value pairs) is sent in the URL of a GET request:
§ /test/demo_form.php?name1=value1&name2=value2
§ Parameters remain in browser history
• POST is used to send data to a server to create/update a resource
§ The data sent to the server with POST is stored in the request body of the HTTP request
§ POST /test/demo_form.php HTTP/1.1
§ Host: w3schools.com
§ name1=value1&name2=value2
§ Parameters are not saved in browser history
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Cookie Workings
setcookie(name,value,expire,path,domain) creates cookies.
<?php
setcookie("uname", $_POST["name"], time()+36000);
?>
<html>
NOTE:
<body>
setcookie() must appear
<p>
Dear <?php echo $_POST["name"] ?>,
a cookie was set on this
BEFORE <html> (or
any output) as it’s part
of the header
page! The cookie will be active when the client has sent the
cookie back to the server.
</p>
information sent with
the page.
</body>
</html>
view the output page
<html>
<body>
<?php
$_COOKIE
contains all COOKIE data.
if ( isset($_COOKIE["uname"]) )
echo "Welcome " . $_COOKIE["uname"] . "!<br />";
else
isset()
echo "You are not logged in!<br />";
?>
finds out if a cookie is set
</body>
</html>
view the output page
use the cookie name as a
variable
25
Getting Time and Date
date() and time () formats a time or a date.
<?php
//Prints something like: Monday
echo date("l");
date() returns a string
formatted according to the
specified format.
//Like: Monday 15th of January 2003 05:51:38 AM
echo date("l jS \of F Y h:i:s A");
//Like: Monday the 15th
echo date("l \\t\h\e jS");
?>
view the output page
<?php
$nextWeek = time() + (7 * 24 * 60 * 60);
time() returns
current Unix
timestamp
// 7 days; 24 hours; 60 mins; 60secs
'. date('Y-m-d') ."\n";
echo 'Next Week: '. date('Y-m-d', $nextWeek) ."\n";
?>
echo 'Now:
view the output page
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Required Fields in User-Entered Data
A multipurpose script which asks users for some basic contact information and then checks to
see that the required fields have been entered.
<html>
<!-- form_checker.php CS443 -->
<head>
<title>PHP Form example</title>
</head>
<body>
<?php
/*declare some functions*/
Print Function
function print_form($f_name, $l_name, $email, $os)
{
?>
<form action="form_checker.php" method="post">
First Name: <input type="text" name="f_name" value="<?php echo $f_name?>" /> <br/>
Last Name <b>*</b>:<input type="text" name="l_name" value="<?php echo $l_name?>" /> <br/>
Email Address <b>*</b>:<input type="text" name="email" value="<?php echo $email?>" /> <br/>
Operating System: <input type="text" name="os" value="<?php echo $os?>" /> <br/><br/>
<input type="submit" name="submit" value="Submit" /> <input type="reset" />
</form>
<?php
}
//** end of "print_form" function
27
Check and Confirm Functions
function check_form($f_name, $l_name, $email, $os)
{
if (!$l_name||!$email){
echo "<h3>You are missing some required fields!</h3>";
print_form($f_name, $l_name, $email, $os);
}
else{
confirm_form($f_name, $l_name, $email, $os);
}
}
//** end of "check_form" function
function confirm_form($f_name, $l_name, $email, $os)
{
?>
<h2>Thanks! Below is the information you have sent to us.</h2>
<h3>Contact Info</h3>
<?php
echo "Name: $f_name $l_name <br/>";
echo "Email: $email <br/>";
echo "OS: $os";
}
//** end of "confirm_form" function
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Main Program
/*Main Program*/
if (!$_POST["submit"])
{
?>
<h3>Please enter your information</h3>
<p>Fields with a "<b>*</b>" are required.</p>
<?php
print_form("","","","");
}
else{
check_form($_POST["f_name"],$_POST["l_name"],$_POST["email"],$_POST["os"]);
}
?>
</body>
</html>
view the output page
29
Learning Outcomes
In the lecture you have learned
§ What is PHP and what are some of its workings.
§ 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.
30
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