Bài giảng Web technologies and e-Services - Bài 5, Phần 1: PHP - Trường Đại học Bách khoa Hà Nội

PHP

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

2

Introduction to PHP

• Server-side programming tries to avoid the drawbacks

▪ 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.

• 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

Introduction to 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

▪ free, open-source

▪ 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

4

Basic PHP syntax

<html>

<head><title>Hello World</title></head>

<body>

A PHP scripting block always starts with <?php

and ends with ?>. A PHP scripting block can be

placed (almost) anywhere in an HTML document.

This is going to be ignored by the PHP interpreter.

<?php echo 'While this is going to be parsed.';

?>

print and echo

for output

This will also be ignored by the PHP preprocessor.

<?php print('Hello and welcome to my

page!');

?>

<?php

//This is a comment

/*

This is

a comment

block

*/

a semicolon (;)

at the end of each

statement

// for a single-line comment

?>

/* and */ for a large

comment block.

</body>

</html>

view the output page

The server executes the print and echo statements, substitutes output.

Scalars

<body>

<?php

$foo = true; if ($foo) echo "It is TRUE! \n";

$txt='1234'; echo "$txt \n";

$a = 1234; echo "$a \n";

$a = -123;

echo "$a \n";

$a = 1.234;

echo "$a \n";

$a = 1.2e3;

echo "$a \n";

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).

$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 = <<<EOD

Example of string

spanning multiple lines

using “heredoc” syntax.

EOD;

Four scalar types:

boolean

true or false

integer,

float,

echo $str;

?>

floating point numbers

string

</body>

</html>

single quoted

double quoted

view the output page

Arrays

<?php

$arr = array("foo" => "bar", 12 => true);

echo $arr["foo"]; // bar

array()= creates arrays

key = either an integer or a string.

value = any PHP type.

echo $arr[12];

?>

// 1

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); }

$arr[] = 56;

$arr["x"] = 42; // adds a new element

unset()removes a

key/value pair

// the same as $arr[13] = 56;

array_values()

makes reindexing effect

(indexing numerically)

unset($arr[5]); // removes the element

unset($arr);

// deletes the whole array

$a = array(1 => 'one', 2 => 'two', 3 => 'three');

unset($a[2]);

$b = array_values($a);

?>

*Find more on arrays

view the output page

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

// Invalid constant names (they shouldn’t start

constants anywhere in

your script without

regard to scope.

//

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");

?>

Operators

Example

x+=y

x-=y

x*=y

x/=y

Is the same as

x=x+y

x=x-y

x=x*y

x=x/y

• Arithmetic Operators: +, -, *,/ , %, ++, --

• Assignment Operators: =, +=, -=, *=, /=, %=

x%=y

x=x%y

• Comparison Operators: ==, !=, >, <, >=, <=

• 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

<body>

if (condition)

code to be executed if condition

is true;

<?php

$d=date("D");

echo $d, " ";

if ($d=="Fri")

echo "Have a nice weekend! ";

else

code to be executed if condition

is false;

echo "Have a nice day! ";

$x=10;

if ($x==10)

{

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

echo "Hello ";

echo "Good morning ";

}

?>

In this case we get a three letter

string for the day of the week.

</body>

</html>

view the output page

Conditionals: switch

<body>

<!–- switch-cond.php CS443 -->

<?php

Can select one of many sets of lines to execute

$x = rand(1,5); // random integer

echo "x = $x ";

switch ($x)

switch (expression)

{

case label1:

case 1:

echo "Number 1";

code to be executed if expression = label1;

break;

case 2:

echo "Number 2";

break;

case 3:

echo "Number 3";

break;

default:

break;

case label2:

code to be executed if expression = label2;

break;

default:

code to be executed

if expression is different

from both label1 and label2;

break;

echo "No number between 1 and 3";

break;

}

?>

</body>

</html>

view the output page

Looping: while and do-while

Can loop depending on a condition

<body>

<body>

<?php

$i=0;

do

{

<?php

$i=1;

while($i <= 5)

{

$i++;

echo "The number is $i ";

$i++;

}

?>

while($i <= 10);

?>

</body>

</html>

</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)

Looping: for and foreach

Can loop depending on a "counter"

<?php

for ($i=1; $i<=5; $i++)

$a_array = array(1, 2, 3, 4);

{

foreach ($a_array as $value)

echo "Hello World! ";

{

}

?>

$value = $value * 2;

echo "$value \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

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

{

echo "Example function.\n";

functions, functions within functions,

return $retval;

and recursive functions.

}

?>

Can return a value of any type

<?php

function small_numbers()

{

function square($num)

return array (0, 1, 2);

{

}

return $num * $num;

list ($zero, $one, $two) = small_numbers();

}

echo square(4);

?>

echo $zero, $one, $two;

?>

<?php

function takes_array($input)

{

echo "$input[0] + $input[1] = ", $input[0]+$input[1];

}

takes_array(array(1,2));

?>

view the output page

Variable Scope

The scope of a variable is the context within which it is defined.

<?php

$a = 1; /* limited variable scope */

function Test()

{

echo $a;

The scope is local within functions,

/* reference to local scope variable */

and hence the value of $a is

}

undefined in the “echo” statement.

Test();

?>

<?php

$a = 1;

function Test()

$b = 2;

function Sum()

{

static

global

static $a = 0;

echo $a;

$a++;

does not lose

its value.

refers to its

global

version.

global $a, $b;

$b = $a + $b;

}

Test1();

?>

Sum();

echo $b;

?>

view the output page

Including Files

The include() statement includes and evaluates the specified file.

// vars.php

<?php

function foo()

{

$color = 'green';

$fruit = 'apple';

global $color;

?>

include ('vars.php‘);

// test.php

<?php

echo "A $color $fruit";

}

echo "A $color $fruit"; // A

include 'vars.php';

/* 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.

*/

echo "A $color $fruit"; // A 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.

PHP Information

The phpinfo() function is used to output PHP information about the version installed on the server, parameters

selected when installed, etc.

INFO_GENERAL

The configuration line,

php.ini location,

build date,

<!– info.php CS443

Web Server,

<body>

System and more

<?php

// Show all PHP information

phpinfo();

?>

<?php

INFO_CREDITS

INFO_CONFIGURATION Local and master values

PHP 4 credits

for php directives

// Show only the general information

phpinfo(INFO_GENERAL);

INFO_MODULES

Loaded modules

?>

</body>

</html>

INFO_ENVIRONMENT

INFO_VARIABLES

Environment variable

information

All predefined variables

from EGPCS

view the output page

INFO_LICENSE

PHP license information

INFO_ALL Shows all of the above (default)

Server Variables

The $_SERVERarray variable is a reserved variable that contains all server information.

<body>

<?php

echo "Referer: " . $_SERVER["HTTP_REFERER"] . " ";

echo "Browser: " . $_SERVER["HTTP_USER_AGENT"] . " ";

echo "User's IP address: " . $_SERVER["REMOTE_ADDR"];

?>

<?php

echo " ";

echo "<h2>All information</h2>";

foreach ($_SERVER as $key => $value)

{

echo $key . " = " . $value . " ";

$_SERVER info

on php.net

}

?>

</body>

</html>

view the output page

The $_SERVER is a super global variable, i.e. it's available in all scopes of a PHP script.

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/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).

File Workings

<?php

fclose() closes a file.

$myFile = "welcome.txt";

if (!($fh=fopen($myFile,'r')))

exit("Unable to open file.");

while (!feof($fh))

$myFile = "welcome.txt";

$fh = fopen($myFile, 'r');

$theData = fgets($fh);

fclose($fh);

echo $theData;

?>

fgetc()reads a single character

fwrite(), fputs ()

writes a string with and without \n

{

$x=fgetc($fh);

echo $x;

}

view the output page

<?php

fclose($fh);

?>

feof()determines if the end is

$myFile = "testFile.txt";

$fh = fopen($myFile, 'a') or

die("can't open file");

$stringData = "New Stuff 1\n";

fwrite($fh, $stringData);

$stringData = "New Stuff 2\n";

fwrite($fh, $stringData);

fclose($fh);

view the output page

true.

fgets()reads a line of data

<?php

$lines = file('welcome.txt');

foreach ($lines as $l_num => $line)

{

echo "Line #{$l_num}:“

.$line.” ”;

file()reads entire file into an

array

?>

view the output page

}

?>

view the output page