Microsoft PowerPoint - PHP

Intro to PHP – Page 1 of 43CSCI 2910 – Client/Server-Side Programming

CSCI 2910

Client/Server-Side Programming

Topic: Intro to PHP

Reading: Chapters 1 and 2

Intro to PHP – Page 2 of 43CSCI 2910 – Client/Server-Side Programming

Today’s Goals

Today’s lecture will cover:

• Differences between server-side and client-

side operation

• Format of a PHP file

• Syntax of PHP code and similarities

between PHP code and JavaScript code

• Data types

Intro to PHP – Page 3 of 43CSCI 2910 – Client/Server-Side Programming

Web Scripting with PHP

PHP has many benefits:

• Open Source

• Flexible for integration with HTML – HTML easily

supports the use of the PHP scripting tags

• Suited to complex projects – database support, vast

libraries, and the power of the server allow PHP to

satisfy very complex programming needs.

• Fast at running scripts – Even though PHP is a

scripting language, the architecture of the scripting

engine provides for fast execution.

• Platform and O/S portable – PHP runs on a variety of

different platforms and operating systems

Intro to PHP – Page 4 of 43CSCI 2910 – Client/Server-Side Programming

General Format of a PHP File

• A block of PHP script is embedded within an

HTML file using the <?php and ?> tags.

• Can also use <script language="PHP"> and

</script>

• The PHP script engine does not like the tag

<?xml version="1.0" encoding="ISO-8859-1"?>

– Engine is interpreting <? ... ?> as executable script

– Remove them from your XML template to create a

PHP template.

– Could use PHP script to generate <?xml> tag

Intro to PHP – Page 5 of 43CSCI 2910 – Client/Server-Side Programming

General Format of a PHP File

(continued)

• Just like JavaScript, whitespace is ignored.

• Just like JavaScript, end lines with

semicolon (;).

• Unlike JavaScript, PHP code is executed at

server and replaced with resulting output.

• The file must have the extension ".php".

Server needs this in order to know to run the

file through the PHP script engine before

sending output to client.

Intro to PHP – Page 6 of 43CSCI 2910 – Client/Server-Side Programming

PHP "Hello, World!"

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<head>

<title>Simple XHTML Document</title>

</head>

<body>

<h1>

<?php

print "Hello, World!";

</h1>

</body>

</html>

Intro to PHP – Page 7 of 43CSCI 2910 – Client/Server-Side Programming

JavaScript "Hello, World!"

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

<head>

<title>Simple XHTML Document</title>

</head>

<body>

document.writeln("Hello, World!");

</script>

</h1>

</body>

</html>

Intro to PHP – Page 8 of 43CSCI 2910 – Client/Server-Side Programming

The Difference – "View Source"

Intro to PHP – Page 9 of 43CSCI 2910 – Client/Server-Side Programming

PHP Comments

• As in JavaScript, there are two methods for

inserting comments into your code. They

are:

– Block comments

– End of line comments

• We don't need to comment out code for

browsers since code is executed on server.

Intro to PHP – Page 10 of 43CSCI 2910 – Client/Server-Side Programming

Block Comments

/* This is a block comment. It

is surrounded by the

slash/asterisk and

asterisk/slash that indicate the

beginning and ending of a

comment. A block comment may

span multiple lines. */

Intro to PHP – Page 11 of 43CSCI 2910 – Client/Server-Side Programming

End of Line Comments

// This is an end of line comment.

// Everything from the double

// slashes to the end of the line

// is ignored.

// To use this method over

// multiple lines, each line must

// have its own set of double

// slashes.

# This is also an end of line

# comment

Intro to PHP – Page 12 of 43CSCI 2910 – Client/Server-Side Programming

Outputting Results

• Just like JavaScript, there are a number of

ways to output results that are to become part

of the HTML file.

• The earlier example uses the print command

to output a string.

• print can also be used to output values or

variables.

• The following slide presents examples of valid

print statements.

Intro to PHP – Page 13 of 43CSCI 2910 – Client/Server-Side Programming

print Examples

print "Hello, World";

print 123; // Outputs "123"

$outputString = "Hello, World!";

print $outputString;

Intro to PHP – Page 14 of 43CSCI 2910 – Client/Server-Side Programming

echo Statement

• The echo statement similar to print

• echo, however, can take on a sequence of

arguments separated by commas.

• Example:

$outputString = "The answer is ";

echo $outputString, 42, "!";

• This outputs "The answer is 42!"

• print cannot combine elements like this.

Intro to PHP – Page 15 of 43CSCI 2910 – Client/Server-Side Programming

Escape Characters

• Because of the number of reserved characters in

PHP, escaping is necessary.

• Characters are escaped by preceding them with a

backslash (\).

• Characters that need escaped include ', ", \, $, and ?.

• Whitespace including carriage returns are allowed as

part of a string, but they are then output as part of the

string. Of course, in HTML, carriage returns are

considered whitespace and are ignored.

• As in JavaScript, single quotes can be used without

escaping within double quoted strings and vice versa.

Intro to PHP – Page 16 of 43CSCI 2910 – Client/Server-Side Programming

Printing Characters Not Available on Keyboard

• Escaping can also be used to display

ISO-8859-1 characters that are not present on the

keyboard.

• This is done by taking the ISO-8859-1 hex value and

placing it after "\x".

• The ISO-8859-1 hex values can be found using the

Character Map application found in Accessories Æ

System Tools.

• For example, the character "¼" has the hexadecimal

ISO-8859-1 value bc

. This can be represented with

\xbc.

• print "\xbc tsp" prints the string "¼ tsp"

Intro to PHP – Page 17 of 43CSCI 2910 – Client/Server-Side Programming

In-Class Exercise

• Earlier it was stated that the PHP script engine does

not like the tag

<?xml version="1.0" encoding="ISO-8859-1"?>.

• How might we still incorporate this tag in the file we

send to the browser without causing problems for

the PHP engine?

Intro to PHP – Page 18 of 43CSCI 2910 – Client/Server-Side Programming

Variable Declarations

• PHP interprets the dollar sign ($) followed by a

letter or an underscore (_) to be a variable name.

• Variables do not need to be declared before you

use them.

• Example: $var1 = 25;

• To help set off a variable identifier within a string,

you can surround it with curly brackets.

• This will become helpful when we start discussing

arrays and objects.

• Example: echo "The value is {$var1}." will display

"The value is 25."

Intro to PHP – Page 19 of 43CSCI 2910 – Client/Server-Side Programming

Data Types

• Scalar types

– boolean

– float

– integer

–string

• Compound types

– array

– object

Intro to PHP – Page 20 of 43CSCI 2910 – Client/Server-Side Programming

Using Scalar Types

• A boolean variable can be assigned only

values of true or false.

$answer = false;

$finished = true;

• An integer is a whole number (no decimal

point)

$age = 31;

Intro to PHP – Page 21 of 43CSCI 2910 – Client/Server-Side Programming

Using Scalar Types (continued)

• A float has a decimal point and may or may not have

an exponent

$price = 12.34;

$avog_num = 6.02e23; //6.02x10^23

• A string is identified as a sequence of characters

$name = "John Smith";

• Strings can be concatenated using a dot (.)

$name = "John" . " Smith";

Intro to PHP – Page 22 of 43CSCI 2910 – Client/Server-Side Programming

Constants

• Constants associate a name with a scalar value.

• Constants are defined using the function define().

define("PI", 3.141593);

• There are a number of predefined constants. These

include:

– M_E = 2.718281828459

– M_PI = 3.1415926535898

– M_2_SQRTPI = 1.1283791670955 (Square root of pi)

– M_1_PI = 0.31830988618379 (Square root of 1/pi)

– M_SQRT2 = 1.4142135623731 (Square root of 2)

– M_SQRT1_2 = 0.70710678118655 (Square root of ½)

Intro to PHP – Page 23 of 43CSCI 2910 – Client/Server-Side Programming

Arithmetic Operators

$y will contain 2

$y = 14 % 3;

Modulo%

$y will contain 8

$y = 7;

$y++;

Increment++

$y will contain 6

$y = 7;

$y--;

Decrement--

$y will contain 16

$z = 4;

$y = $z * 4;

Multiplication*

$y will contain 7

$y = 14 / 2;

Division/

$y will contain 2

$y = 3;

$y = $y – 1;

Subtraction–

$y will contain 4

$y = 2 + 2;

Addition+

ResultExampleOperationOperator

Intro to PHP – Page 24 of 43CSCI 2910 – Client/Server-Side Programming

Bitwise Logical Operations

• ~ Bitwise NOT operator: Inverts each bit of the

single operand placed to the right of the

symbol

• & Bitwise AND: Takes the logical-bitwise AND

of two values

• | Bitwise OR operator: Takes the logical-

bitwise OR of two values

• ^ Bitwise XOR: Takes the logical-bitwise

exclusive-OR of two values

Intro to PHP – Page 25 of 43CSCI 2910 – Client/Server-Side Programming

Bitwise Shift Operations

• << Left shift: Shifts the left operand left by the

number of places specified by the right

operand filling in with zeros on the right side.

• >> Sign-propagating right shift: Shifts the left

operand right by the number of places

specified by the right operand filling in with

the sign bit on the left side.

• >>> Zero-fill right shift operator: Shifts the

left operand right by the number of places

specified by the right operand filling in with

zeros on the left side.

Intro to PHP – Page 26 of 43CSCI 2910 – Client/Server-Side Programming

Flow Control

• As in JavaScript, flow control consists of a

number of reserved words combined with

syntax to allow the computer to decide

which parts of code to execute, which to

jump over, and which to execute multiple

times.

• For the most part, the flow control that you

learned for JavaScript is the same for PHP.

Intro to PHP – Page 27 of 43CSCI 2910 – Client/Server-Side Programming

If-Statement

• The code below represents the syntax of a

typical if-statement:

if ($grade > 93)

print "Student's grade is A";

• If grade was 93 or below, the computer

would simply skip this instruction.

Intro to PHP – Page 28 of 43CSCI 2910 – Client/Server-Side Programming

If-Statement (continued)

• Just like JavaScript, multiple instructions

may be grouped using curly brackets. For

example:

if ($grade > 93)

{

print "Student's grade is A";

$honor_roll_value = true;

}

Intro to PHP – Page 29 of 43CSCI 2910 – Client/Server-Side Programming

If-Statement (continued)

• As in JavaScript, the programmer can string together

if-statements to allow the computer to select from one

of a number of cases using elseif and else. (Note that

JavaScript allows else if while PHP uses elseif.)

• For example:

if ($grade > 93)

print "Student's grade is an A";

elseif ($grade > 89)

print Student's grade is an A-";

else

print "Student did not get an A";

Intro to PHP – Page 30 of 43CSCI 2910 – Client/Server-Side Programming

Comparison Operators

• > Returns true if the first value is greater

than the second

• >= Returns true if the first value is greater

than or equal to the second

• < Returns true the first value is less than

the second

• <= Returns true if the first value is less than

or equal to the second

• == Returns true if first value is equal to second

• != Returns true if first value is not equal to

second

Intro to PHP – Page 31 of 43CSCI 2910 – Client/Server-Side Programming

Logical Operators

• ! Returns true if its operand is zero or

false

• && Returns false if either operand is zero

or false

• || Returns false if both operands are zero

or false

Intro to PHP – Page 32 of 43CSCI 2910 – Client/Server-Side Programming

Switch-Statement

• The switch statement can be used as an

alternative to the if, elseif, else method.

switch($menu)

{

case 1:

print "You picked one";

break;

case 2:

print "You picked two";

break;

default:

print "You did not pick one or two";

break;

}

Intro to PHP – Page 33 of 43CSCI 2910 – Client/Server-Side Programming

Switch-Statement (continued)

• Note that if a break is not encountered at the

end of a case, the processor continues through

to the next case.

• Example: If $var1=1, it will print both lines.

switch($var1)

{

case 1:

print "The value was 1";

default:

print "Pick another option";

break;

}

Intro to PHP – Page 34 of 43CSCI 2910 – Client/Server-Side Programming

While-loop

• PHP uses the while-loop just like

JavaScript.

• Like the if-statement, this format also uses a

condition placed between two parenthesis

• As long as the condition evaluates to true,

the program continues to execute the code

between the curly brackets in a round-robin

fashion.

Intro to PHP – Page 35 of 43CSCI 2910 – Client/Server-Side Programming

While-loop (continued)

• Format:

while(condition)

{

statements to execute

}

• Example:

$count = 1;

while($count < 72)

{

print "$count ";

$count++;

}

Intro to PHP – Page 36 of 43CSCI 2910 – Client/Server-Side Programming

do … while loop

• The do … while loop works the same as a while

loop except that the condition is evaluated at

the end of the loop rather than the beginning

• Example:

$count = 1;

{

print "$count ";

$count++;

}while($count < 72);

Intro to PHP – Page 37 of 43CSCI 2910 – Client/Server-Side Programming

for-loop

• In the two previous cases, a counter was

used to count our way through a loop.

• This task is much better suited to a for-loop.

for ($count = 1; $count < 72; $count++)

{

print "$count ";

}

• A "break" can be used to break out of a loop

earlier.

Intro to PHP – Page 38 of 43CSCI 2910 – Client/Server-Side Programming

In-Class Exercise

Convert the JavaScript shown below to PHP?

<!--

value = 34.5;

for(i = 0; i < 10; i++)

{

document.writeln("34.5/(2^" + i + ") is " + value);

document.writeln("<br />");

value = value/2;

}

//-->

</script>

Intro to PHP – Page 39 of 43CSCI 2910 – Client/Server-Side Programming

Type Conversion

• Different programming languages deal with

variable types in different ways. Some are strict

enforcing rules such as not allowing an integer

value to be assigned to a float.

• The process of converting from one data type to

another is called "casting".

• To convert from one type to another, place the

type name in parenthesis in front of the variable to

convert from.

• In some cases, there are functions that perform

the type conversion too.

Intro to PHP – Page 40 of 43CSCI 2910 – Client/Server-Side Programming

Some Examples of Type Conversion

• $ivar = (int) $var;

• $ivar = (integer) $var;

• $ivar = intval($var);

• $bvar = (bool) $var;

• $bvar = (boolean) $var;

• $fvar = (float) $var;

• $fvar = floatval($var);

• $svar = (string) $var;

• $svar = stringval($var);

Intro to PHP – Page 41 of 43CSCI 2910 – Client/Server-Side Programming

Examples of Type Conversion

(continued)

0"foo"true0"foo"

6"6 feet"true6"6 feet"

10"10"true10"10"

0"0"false0"0"

3.8"3.8"true33.8

0"0"false00

0""false0false

1"1"true1true

0""false0null

Cast to floatCast to stringCast to boolCast to intValue

Intro to PHP – Page 42 of 43CSCI 2910 – Client/Server-Side Programming

Type Conversion (continued)

• PHP can automatically convert types too.

• If a variable is used as if it were a different type,

the PHP script engine assumes a type

conversion is needed and does it for you.

• Examples:

$var = "100" + 15; // var$ set to integer = 115

$var = "100" + 15.0; // var$ set to float = 115

$var = 15 + " bugs"; // var$ set to integer = 15

$var = 15 . " bugs"; // var$ set to string = "15 bugs"

Intro to PHP – Page 43 of 43CSCI 2910 – Client/Server-Side Programming

In-Class Exercise

Identify the errors in the following PHP script.

<?php

strvar1 = "<h1 align="center">Integer

Squares from 0 to 9</h1>"

prints strvar

prints "<ul>"

for(i = 0; i < 9; i+)

{

isquared = i * i

prints "<li>Square root of " + i +

" is " + isquared + "</li>"

}

prints "</ul>"