WEB TECHNOLOGY (PHP)

Unit - I

INTRODUCTION

1. Origin of PHP

 PHP is a recursive acronym for "PHP: Hypertext Preprocessor".

 PHP is a server side scripting language that is embedded in HTML. It is used to manage
dynamic content, databases, session tracking, even build entire e- commerce sites.
 It is integrated with a number of popular databases, including My SQL, Postgre SQL,
Oracle, Sybase, Informix, and Microsoft SQL Server.
 PHP is pleasingly zippy in its execution, especially when compiled as an Apache module
on the Unix side. The My SQL server, once started, executes even very complex queries
with huge result sets in record-setting time.
 PHP supports a large number of major protocols such as POP3, IMAP, and LDAP. PHP4
added support for Java and distributed object architectures (COM and CORBA), making
n-tier development a possibility for the first t.
 PHP is forgiving: PHP language tries to be as forgiving as possible.
 PHP Syntax is C-Like.
 Common uses of PHP.

2. PHP is better than its alternatives

 It is faster to code and faster to execute.

 The same PHP code runs unaltered on different Web servers and different
operation systems.

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  Additionally, functionality that is standard with PHP is an add-on in
other environments. A more detailed argument follows.
 PHP is free. Anyone may visit the PHP Web site and download the complete source
code. Binaries are also available for Windows. The result is easy entry into the
experience. There is very little risk in trying PHP, and its license allows the code to be
used to develop works with no royalties.

 This is unlike products such as Allaire's Cold Fusion or Every ware's Tango
Enterprise that charge thousands of dollars for the software to interpret and serve
scripts. Even commercial giants like Netscape and IBM now recognize the
advantages of making source code available.

 PHP runs on UNIX, Windows 98, Windows NT, and the Macintosh. PHP is designed
to integrate with the Apache Web Server.

 Apache, another free technology, is the most popular Web server on the Internet and
comes with source code for UNIX and Windows. Commercial flavors of Apache
like Web Ten and Stronghold support PHP, too.

 But PHP works with other Web servers, including Microsoft's Internet Information
Server. Scripts may be moved between server platforms without alteration. PHP
supports ISAPI to allow for the performance benefits of tightly coupling with Microsoft
Web servers.

3. How PHP works with the web server

 The PHP software works with the web server, which is the software that
delivers web pages to the world.
 When you type a URL into your web browser‘s address bar, you‘re sending
a message to the web server at that URL, asking it to send you an HTML file.The web
server responds by sending the requested file. Your browser reads the HTML file and

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 displays the web page.

 You also request a file from the web server when you click a link in a webpage. In
addition, the web server processes a file when you click a web page button that submits
a form. This process is essentially the same when PHP is installed. You request a file,
the web server happens to be running PHP, and it sends HTML back to the browser,
thanks to the programming in PHP.
 More specifically, when PHP is installed, the web server is configured to
expect certain file extensions to contain PHP language statements.
 Often the extension is .php or .phtml, but any extension can be used. When the web
server gets a request for a file with the designated extension, it sends the HTML
statements as is, but PHP statements are processed by the PHP software before they‘re
sent to the requester.
 When PHP language statements are processed, only the output, or anything printed
to the screen is sent by the web server to the web browser.
 The PHP language statements, those that don‘t produce any output to the screen,
aren‘t included in the output sent to the browser, so the PHP code is not normally seen
by the user.
 For instance, in this simple PHP statement, <?php is the PHP opening tag, and ?>
is the closing tag.
 <?php echo "<p>Hello World</p>"; ?>
 Here, echo is a PHP instruction that tells PHP to output the upcoming text. The
PHP software processes the PHP statement and outputs the following:
 <p>Hello World</p>
 That regular HTML statement is delivered to the user‘s browser. The browser
interprets the statement as HTML code and displays a web page with one
paragraph
— Hello World.

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  The PHP statement isn‘t delivered to the browser, so the user never sees any
PHP statements. PHP and the web server must work closely together.

4. Hardware and Software Requirements and installation

These are the following the software requirements

 WAMP Server
 LAMP Server
 MAMP Server
 XAMPP Server
All these types of software automatic configure inside operating system after installation it
having PHP, My SQL, Apache and operating system base configuration file, it doesn't need to
configure manually.

Server Stands for

WAMP Microsoft window o/s, Apache Mysql PHP LAMP

Linux Operating System Apache Mysql

PHPMAMP Mac os Apache Mysql PHP

XAMPP x-os(cross operating system) Apache Mysql PHP Perl

Hardware Requirements

 If you would like to use a dedicated hosting server for running PHPKB Knowledge Base
Software or host it on a local server, you can use hardware requirements and example
specifications below for a reference.
 Recommended Hardware Specifications

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  On small instances, server load is primarily driven by peak visitors however you may
use the following specifications for optimal performance.
 5 Concurrent Users 25 Concurrent Users 50 Concurrent Users
 1 GHz CPU
 2 GB RAM
 1 GB disk space
 Dual 2 GHz CPU
 4 GB RAM
 1 GB disk space
 Dual 2.6 GHz CPU
 8 GB RAM
 4 GB disk space

The PHP Installer

 Although an installer is available from php.net, I would recommend the manual

installation if you already have a web server configured and running.

 Manual Installation

 Manual installation offers several benefits:

 backing up, reinstalling, or moving the web server can be achieved in

seconds (see 8 Tips for Surviving PC Failure) and

 you have more control over PHP and Apache configuration.

Step 1: Download the files

 Download the latest PHP 5 ZIP package from www.php.net/downloads.php

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  As always, virus scan the file and check its MD5 checksum using a tool such as f sum.
Step 2: Extract the files

 We will install the PHP files to C:\php, so create that folder and extract the contents
of the ZIP file into it.

 PHP can be installed anywhere on your system, but you will need to change the
paths referenced in the following steps.

Step 3: Configure php.ini

 Copy C:\php\php.ini-development to C:\php\php.ini. There are several lines you

will need to change in a text editor (use search to find the current setting).

 Where applicable, you will need to remove the leading semicolon

to uncomment these setting.

Define the extension directory:

extension_dir = "C:/php/ext"

Enable extensions.

This will depend on the libraries you want to use, but the following extensions should be
suitable for the majority of applications:

extension=curl

extension=gd2

extension=mbstring

extension=mysql

extension=pdo_mysql

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 extension=xmlrpc

If you want to send emails using the PHP mail() function, enter the details of anSMTP server
(your ISP‘s server should be suitable):

[mail function]

; For Win32 only.

SMTP =

mail.myisp.com

smtp_port = 25

; For Win32 only.

sendmail_from = my@emailaddress.com

Step 4: Add C:\php to the path environment variable

 To ensure Windows can find PHP, you need to change the path environmentvariable.

 Open Settings, type ‗environment variables‘ into the search field and openthe result.

 Select the ―Advanced‖ tab, and click the ―Environment Variables‖ button.

 Scroll down the System variables list and click on ―Path‖ followed by the ―Edit‖
button. Click ―Edit text‖ and add ;C:\php to the end of the Variable value line
(remember the semicolon).

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 5. PHP pros and cons

5.1. PHP : past, present, future(PHP3.O,PHP4.O,PHP5.O)

 PHP3 is oldest stable version and it was pure procedural
language constructive like C

 Whereas PHP4 have some OOPs concept added like class and object
withnew functionality

 PHP5 approximately all major oops functionality has been added along withbelow thing
 Implementation of exceptions and exception handling
 Type hinting which allows you to force the type of a specific argument
 Overloading of methods through the call function

 Full constructors and destructors etc through a constuctor and

destructor function

 autoload function for dynamically including certain include files

depending on the class you are trying to create.

 Finality : can now use the final keyword to indicate that a method cannot be
overridden by a

 child. You can also declare an entire class as final which prevents it from having
any children at all.

 Interfaces & Abstract Classes

 Passed by Reference :
 An clone method if you really want to duplicate an object

 Numbers of Functions Deprecated or removed in PHP 5.x like

ereg,ereg_replace,magic_quotes, session_register,register_globals, split(),
call_user_method() etc

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 6 .Strength of Php

Supports database connectivity. PHP can access over 20 different databases including My Sql,
Oracle, and MS Access.
Supports sessions. PHP can generate unique session IDs. The ID follows the user during
a single session on a web site. This simplifies creating shopping cart applications and
tracking user's behaviors.
Eliminates client configuration problems. With PHP there is no need to worry if
the client has the appropriate software installed, since the application is executed on
the server.
Reduces development time. Even a newcomer can begin developing PHP
applications in hours. Yet PHP contains many advanced features for professional
programmers.
Maintains source code security. The user does not see your source code as they do
with JavaScript.

7. Basic PHP Development7. 1 How

PHP script work
 PHP always start with a browser making a request for a web page.
 This request is going to hit the web server.
 The web server will then analyze it and determine what to do with it.
 If the web server determines that the request is for a PHP file (often index.php
), it‘ll pass that file to the PHP interpreter.

 The PHP interpreter will read the PHP file, parse it (and other included files) and then
execute it.
 Once the PHP interpreter finishes executing the PHP file, it‘ll return an output. The web
server will take that output and send it back as a response tothe browser.

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 7. 2 Basic PHP syntax
 PHP script starts with the <?php and ends with the ?> tag.
 The PHP delimiter <?php and ?> in the following example simply tells the PHP engine to
treat the enclosed code block as PHP code, rather than simple HTML.

Syntax :

<?php

// Some code to be executed echo

"Hello, world!";

?>

 Every PHP statement end with a semicolon (;) — this tells the PHP engine that the
end of the current statement has been reached.

Comment Lines

 A comment is simply text that is ignored by the PHP engine. The purpose of comments
is to make the code more readable.

 It may help other developer (or you in the future when you edit the source code)
to understand what you were trying to do with the PHP.

 PHP support single-line as well as multi-line comments.

 To write a single-line comment either start the line with either two slashes (//)or a hash

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 symbol (#).
For example:

<?php

// This is a single line comment

# This is also a single line comment echo "Hello,

world!";

?>

However to write multi-line comments, start the comment with a slash followed by an asterisk (/*)
and end the comment with an asterisk followed by a slash (*/).

Case Sensitivity in PHP

Variable names in PHP are case-sensitive.

As a result the variables $color, $Color and $COLOR are treated as three different variables.

<?php

// Assign value to variable

$color = "blue";

// Try to print variable value

echo "The color of the sky is " . $color . "<br>"; echo "The

color of the sky is " . $Color . "<br>"; echo "The color of

the sky is " . $COLOR . "<br>";

?>

7.3 PHP variables

 All variables in PHP are denoted with a leading dollar sign ($).

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  The value of a variable is the value of its most recent assignment.
 Variables are assigned with the = operator, with the variable on the left-handside and
the expression to be evaluated on the right.
 Variables can, but do not need, to be declared before assignment.
 Variables in PHP do not have intrinsic types - a variable does not know in
advance whether it will be used to store a number or a string of characters.
 Variables used before they are assigned have default values.
 PHP does a good job of automatically converting types from one to another
when necessary.
 PHP variables are Perl-like.

7.4. PHP Data types

PHP has a total of eight data types which we use to construct our variables –

 Integers − are whole numbers, without a decimal point, like 4195.

 Doubles − are floating-point numbers, like 3.14159 or 49.1.
 Booleans − have only two possible values either true or false.
 NULL − is a special type that only has one value: NULL.
 Strings − are sequences of characters, like 'PHP supports string operations.'
 Arrays − are named and indexed collections of other values.
 Objects − are instances of programmer-defined classes, which can package up
both other kinds of values and functions that are specific to the class.
 Resources − are special variables that hold references to resources external to
PHP (such as database connections).

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 Integers

They are whole numbers, without a decimal point, like 4195.

They are the simplest type.

They correspond to simple whole numbers, both positive and negative. Integers can be
assigned to variables, or they can be used in expressions, like

$int_var = 12345;

$another_int = -12345 + 12345;

Integer can be in decimal (base 10), octal (base 8), and hexadecimal (base 16)format.

Decimal format is the default, octal integers are specified with a leading 0,and
hexadecimals have a leading 0x.

Doubles

They like 3.14159 or 49.1. By default, doubles print with the minimum number of
decimal places needed.

For example, the code

<?php

$many = 2.2888800;

$many_2 = 2.2111200;

$few = $many + $many_2;

print("$many + $many_2 = $few <br>");

?>

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 It produces the following browser output −

2.28888 + 2.21112 = 4.5

Boolean

They have only two possible values either true or false.

PHP provides a couple of constants especially for use as Booleans: TRUE and FALSE,
which can be used like so −

if (TRUE)

print("This will always print<br>");

else

print("This will never print<br>"

NULL

NULL is a special type that only has one value: NULL.

To give a variable the NULL value, simply assign it like this −

$my_var = NULL;

The special constant NULL is capitalized by convention, but actually it is case

insensitive; you could just as well have typed −

$my_var = null;

A variable that has been assigned NULL has the following properties

− It evaluates to FALSE in a Boolean context.

It returns FALSE when tested with IsSet() function.

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 Strings

They are sequences of characters, like "PHP supports string operations". Following are valid
examples of string

$string_1 = "This is a string in double quotes";

$string_2 = 'This is a somewhat longer, singly quoted string';

$string_39 = "This string has thirty-nine characters";

$string_0 = ""; // a string with zero characters.

8.Displaying Type Information with var_dump():

var_dump() provides information about all the types contained within the variable,
as well as about the variable itself.

$testing = 5;

var_dump( $testing )

Output

int(5)

7.5. Displaying type information

This function displays structured information about one or moreexpressions that

includes its type and value.
Arrays and objects are explored recursively with values indentedto show
structure.

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 Example #1 var_dump()

<?php
$a = array(1, 2, array("a", "b", "c"));
var_dump($a);
?>

The above example will output:

array(3) {
[0]=>
int(1)
[1]=>
int(2)
[2]=>
array(3) {
[0]=>
string(1) "a"
[1]=>
string(1) "b"
[2]=>
string(1) "c"
}
}
<?php

$b = 3.1;

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 $c = true;
var_dump($b, $c);

?>

The above example will output:

float(3.1)
bool(true)

7.6. Testing for a Specific Data Type

 PHP provides a special function corresponding to each data type.

 These functions accept a variable or value and return a Boolean

Function

is_array()

Returns true if the argument is an array

is_bool()

Returns true if the argument is boolean

is_double()

Returns true if the argument is a double

is_int()

Returns true if the argument is an integer

is_object()

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 Returns true if the argument is an object
is_string()

Returns true if the argument is a string

is_null()

Returns true if the argument is null

is_resource()

Returns true if the argument is a resource

7.7. Operators

 PHP Operator is a symbol i.e used to perform operations on operands

 In simple words, operators are used to perform operations on variables orvalues.
For example:
$num=10+20;//+ is the operator and 10,20 are operands
In the above example, + is the binary + operator, 10 and 20 are operands and
$num is variable.

PHP Operators can be categorized in following forms:

a. Arithmetic Operators
b. Assignment Operators
c. Bitwise Operators
d. Comparison Operators
e. Incrementing/Decrementing Operators
f. Logical Operators
g. String Operators

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 h. Array Operators
Arithmetic operators:

The PHP arithmetic operators are used to perform common arithmetic operationssuch as
addition, subtraction, etc. with numeric values.

Operator Name Example Explanation

+ Addition $a + $b Sum of operands

- Subtraction $a - $b Difference of operands

* Multiplication $a * $b Product of operands

/ Division $a / $b Quotient of operands

% Modulus $a % $b Remainder of operands

** Exponentiation $a ** $b $a raised to the power $b

Assignment Operators

The assignment operators are used to assign value to different variables. The basicassignment
operator is "=".

Operator Name Example Explanation

= Assign $a = $b The value of right operand is assigned to the

left operand.

+= Add then Assign $a += $b Addition same as $a = $a + $b

-= Subtract then Assign $a -= $b Subtraction same as $a = $a - $b

*= Multiply then Assign $a *= $b Multiplication same as $a = $a * $b

/= Divide then Assign

(quotient) $a /= $b Find quotient same as $a = $a / $b

%= Divide then Assign

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 (remainder) $a %= $b Find remainder same as $a = $a % $b
Bitwise operators

The bitwise operators are used to perform bit-level operations on operands. These operators allow
the evaluation and manipulation of specific bits within the integer.

Operator Name Example Explanation

& And $a & $b Bits that are 1 in both $a and $b are set to 1, otherwise 0.

| Or (Inclusive or) $a | $b Bits that are 1 in either $a or $b are set to 1

^ Xor (Exclusive or) $a ^ $b Bits that are 1 in either $a or $b are set to 0.

~ Not ~$a Bits that are 1 set to 0 and bits that are 0 are set to 1

Comparison Operators

Comparison operators allow comparing two values, such as number or string. Below the list
of comparison operators are given:

Operator Name Example Explanation

== Equal $a == $b Return TRUE if $a is equal to $b

=== Identical $a === $b Return TRUE if $a is equal to $b, and they are of
same data type

!== Not identical $a !== $b Return TRUE if $a is not equal to $b, and
they are not of same data type

!= Not equal $a != $b Return TRUE if $a is not equal to $b

<> Not equal $a <> $b Return TRUE if $a is not equal to $b

< Less than $a < $b Return TRUE if $a is less than $b

> Greater than $a > $b Return TRUE if $a is greater than $b

<= Less than or equal to $a <= $b Return TRUE if $a is less than or equal
$b

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 >= Greater than or equal to $a >= $b Return TRUE if $a is greater than orequal
$b

<=> Spaceship $a <=>$b Return -1 if $a is less than

$b Return 0 if $a is equal $b Return 1 if

$a is greater than $b

Incrementing/Decrementing Operators

The increment and decrement operators are used to increase and decrease the valueof a variable.

Operator Name Example Explanation

++ Increment ++$a Increment the value of $a by one, then return $a

$a++ Return $a, then increment the value of $a by one

-- decrement --$a Decrement the value of $a by one, then return $a

$a-- Return $a, then decrement the value of $a by one

Logical Operators

The logical operators are used to perform bit-level operations on operands. These operators allow the
evaluation and manipulation of specific bits within the integer.

Operator Name Example Explanation

and And $a and $b Return TRUE if both $a and $b are

trueOr Or $a or $b Return TRUE if either $a or

$b is true
xor Xor $a xor $b Return TRUE if either $ or $b is true but not both

! Not ! $a Return TRUE if $a is not true

&& And $a && $b Return TRUE if either $a and $b are true

|| Or $a || $b Return TRUE if either $a or $b is true

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 String Operators

The string operators are used to perform the operation on strings. There are twostring operators
in PHP, which are given below:

Operator Name Example Explanation

. Concatenation $a . $b Concatenate both $a and $b

.= Concatenation and Assignment $a .= $b First concatenate $a and $b,

then assign the concatenated string to $a, e.g. $a = $a . $b

Array Operators

The array operators are used in case of array. Basically, these operators are used to compare the
values of arrays.

Operator Name Example Explanation

+ Union $a + $y Union of $a and $b

== Equality $a == $b Return TRUE if $a and $b have same key/value

pair

!= Inequality $a != $b Return TRUE if $a is not equal to $b

=== Identity $a === $b Return TRUE if $a and $b have same key/value

pair of same type in same order

!== Non-Identity $a !== $b Return TRUE if $a is not identical to $b

<> Inequality $a <> $b Return TRUE if $a is not equal to $b

7.7 Variable manipulation

 Variable manipulation is a method of specifying or editing variables in a

computer program.

 Variable manipulation can be used to create dynamic content in HTML and

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 programming languages. However, the method can also be used by an attacker, to
alter data that a browser sends to a Web server. A variable, in this context, is a
string of text symbols and/or numerals that can change, depending on conditions or
on information passed to the program.
 In mathematics, variable manipulation is the process of rearranging a multivariable
equation to express a specific variable as a function of other variables.
 The variable thus singled-out is known as the dependent variable, while the
other variables are called independent variables.
 In this context, a variable is a mathematical quantity whose numerical value can
change, in contrast to constants that have fixed numerical values.

7.8 .Dynamic variables

 PHP allows us to use dynamic variable.

 Dynamic variable is variable variables.
 We can name a variable with the value stored in another variable.
 That is, one variable contains the name of another variable.

Example:
$text = ‗Hello World‘;
$dynamicText = ―text‖;
echo ‗The dynamic ‗.$dynamicText. ‗ is ‗.${$dynamicText};

Output : The dynamic text is Hello World

We can implement it ${$dynamicText} or $$dynamicText .

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 Here we can associate variable to another variable. We can use it as alternative of
associative array and list. The time complexity also less then array and list also.

7.8 String in PHP

 A string is a collection of characters. String is one of the data type

ssupported by PHP.
 The string variables can contain alphanumeric characters. Strings are created when;
 You declare variable and assign string characters to it
 You can directly use them with echo statement.
 String are language construct, it helps capture words.
 Learning how strings work in PHP and how to manipulate them will make you a very effective
and productive developer.

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 Unit - II

.Control structures

Control structure allows you to control the flow of code execution in your application.

Generally, a program is executed sequentially, line by line, and a control structure

allows you to alter that flow, usually depending on certain conditions.

PHP supports a number of different control structures:

if
else

elseif

switch

while

do-while

for

foreach

The If statement

The if construct allows you to execute a piece of code if the expression provided along with it
evaluates to true.

Example:

<?php

$age = 50;

if ($age > 30)

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 {

echo "Your age is greater than 30!";

?>

Using the Else clause with if Statement

if the expression evaluates to true. On the other hand, if the expression evaluates to false, it
won't do anything.
More often than not, you also want to execute a different code snippet if the expression
evaluates to false.

Syntax

if (expression)

// code is executed if the expression evaluates to TRUE

else

// code is executed if the expression evaluates to FALSE

Example

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 <?php

$age = 50;

if ($age < 30)

echo "Your age is less than 30!";

else

echo "Your age is greater than or equal to 30!";

?>
Multiple if, nested If Statement

We can consider the elseif statement as an extension to the if-else construct.

If you've got more than two choices to choose from, you can use the elseif statement.

Syntax

if (expression1)

// code is executed if the expression1 evaluates to TRUE

elseif (expression2)

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 {

// code is executed if the expression2 evaluates to TRUE

elseif (expression3)

// code is executed if the expression3 evaluates to TRUE

else

// code is executed if the expression1, expression2 and expression3 evaluates toFALSE, a default
choice
Example

<?php

$age = 50;

if ($age < 30)

echo "Your age is less than 30!";

elseif ($age > 30 && $age < 40)

echo "Your age is between 30 and 40!";

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 }

elseif ($age > 40 && $age < 50)

echo "Your age is between 40 and 50!";

else

echo "Your age is greater than 50!";

?>
Switch Statement

 The switch statement is somewhat similar to the elseif statement which we've just
discussed in the previous section.

 The only difference is the expression which is being checked.

 In the case of the elseif statement, you have a set of different conditions, and
an appropriate action will be executed based on a condition.

 On the other hand, if you want to compare a variable with different values, you can use
the switch statement.

<?php

$favourite_site = 'Code';

switch ($favourite_site) {case

'Business':

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 echo "My favourite site is business.tutsplus.com!";break;

case 'Code':

echo "My favourite site is code.tutsplus.com!";break;

case 'Web Design':

echo "My favourite site is webdesign.tutsplus.com!";break;

case 'Music':

echo "My favourite site is music.tutsplus.com!";break;

case 'Photography':
echo "My favourite site is photography.tutsplus.com!";break;

default:

echo "I like everything at tutsplus.com!";

?>

? Operators

This is called the Ternary Operator, and it's common to several languages,including PHP,
Javascript, Python, Ruby...

$x = $condition ? $trueVal : $falseVal;

// same as:

Example:

if ($condition) {

$x = $trueVal;

} else {

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 $x = $falseVal;

} errorLoops

A Loop is an Iterative Control Structure that involves executing the same

number of code a number of times until a certain condition is met.

12.1 While loop

 They are used to execute a block of code a repeatedly until the set condition gets satisfied
 When to use while loops
 While loops are used to execute a block of code until a certain condition
becomes true.
 You can use a while loop to read records returned from a database query.
 Types of while loops
 Do… while - executes the block of code at least once before evaluating the condition
 While… - checks the condition first. If it evaluates to true, the block of code is
executed as long as the condition is true. If it evaluates to false, the execution of the
while loop is terminated.
While loop
It has the following syntax
<?php
while (condition){
block of code to be executed;
}
?>

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 HERE,
―while(…){…}‖ is the while loop block code
―condition‖ is the condition to be evaluated by the while loop
―block of code…‖ is the code to be executed if the condition gets satisfied How it works

The flow chart shown below illustrates how the while… loop works PHP
Loop and Control Structures
Practical example
The code below uses the while… loop to print numbers 1 to 5.
<?php
$i = 0;
while ($i < 5){
echo $i + 1 . "<br>";
$i++;
}
?>
Output:
1
2
3
4
5
12.2 Do While
The difference between While… loop and Do… while loop is do… while is executed at-least
once before the condition is evaluated.
Let‘s now look at the basic syntax of a do… while loop

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 <?php
do{
block of code to be executed
}
?>
while(condition);HERE,
―do{…} while(…)‖ is the do… while loop block code ―condition‖ is the
condition to be evaluated by the while loop
―block of code…‖ is the code that is executed at least once by the do… while loop How it works

The flow chart shown below illustrates how the while… loop works PHP
Loop and Control Structures
We are now going to modify the while… loop example and implement it using the do… while
loop and set the counter initial value to 9.
The code below implements the above modified example
<?php
$i = 9;
do{
echo "$i is"." <br>";
}
while($i < 9);
?>
The above code outputs:9
12.3 For Loop

The above code outputs ―21 is greater than 7‖ For loops For... loops execute the
block of code a specified number of times. There are basically two types of for loops;
for
for… each.
Let‘s now look at them separately. For loop It has the following basic syntax

<?php

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 for (initialize; condition; increment){

//code to be executed

}
?>
HERE,
―for…{…}‖ is the loop block
―initialize‖ usually an integer; it is used to set the counter‘s initial value. ―condition‖ the
condition that is evaluated for each php execution. If it evaluates to true then execution of the
for... loop is terminated. If it evaluates to false, the execution of the for... loop continues.
“increment” is used to increment the initial value of counter integer.

String function

They are sequences of characters, like "PHP supports string

operations". Following are valid examples of string

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 $string_1 = "This is a string in double quotes";
$string_2 = 'This is a somewhat longer, singly quoted string';
$string_39 = "This string has thirty-nine characters";
$string_0 = ""; // a string with zero characters.

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