modified from moseley ’s sli desweb applications development. lecture 5 slide 1 lecture 5:...

Modified from Moseley’s slides Web Applications Development. Lecture 5 Slide 1Modified from Moseley’s slides Web Applications Development. Lecture 5 Slide 1

Lecture 5: Introduction to PHP

Instructor: Dr. Mohammad Anwar Hossain


Introduction to PHP

•PHP – history and getting start•PHP - Overview•Variables & Scope•Output •Variable types ; Boolean; Strings •String Functions & Parsers•Screening User Input/Output •Maths functions •Control and flow

Today:


PHP• PHP is a scripting language that allows you to create dynamic

Web pages

• PHP-Hypertext Preprocessor.

Other Names : Personal Home Page, Professional Home Page

• You can embed PHP scripting within normal html coding

• PHP was designed primarily for the Web

• PHP includes a comprehensive set of database access functions

• High performance/ease of learning/low cost


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 August 2004, PHP is used on 16,946,328 Domains, 1,348,793 IP Addresses http://www.php.net/usage.php This is roughly 32% of all

domains on the web.

Brief History of PHP

Modified from Moseley’s slides Web Applications Development. Lecture 5 Slide 6

Why is PHP used?

1. Easy to UseCode 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>


Why is PHP used?

2. Cross PlatformRuns 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?

PHP

Software Free

Platform Free (Linux)

Development Tools Free

PHP Coder, jEdit

3. Cost BenefitsPHP 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.


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.

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

<?php echo “Hello World”; ?>PHP CODE HTMLHTML


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></head><body><?phpecho "Hello World!";?></body></html>

Copy the code onto your web server and save it as “test.php”.

You should see “Hello World!” displayed.

Notice that the semicolon is used at the end of each line of PHP code to signify a line break. Like HTML, PHP ignores whitespacebetween lines of code. (An HTML equivalent is <BR>)


Getting Started

3. Using conditional statements• Conditional statements are very useful for displaying

specific content to the user. The following example shows how to display content according to the day of the week.

<?php$today_dayofweek = date(“w”);

if ($today_dayofweek == 4){ echo “Today is Thursday!”; }else{ echo “Today is not Thursday.”;}

?>


Getting Started

3. Using conditional statementsThe if statement checks the value of $today_dayofweek (which is the numerical day of the week, 0=Sunday… 6=Saturday)

If it is equal to 4 (the numeric representation of Thurs.) it will display everything within the first { } bracket after the “if()”.

If it is not equal to 4, it will display everything in the second { } bracket after the “else”.



?>


Getting Started3. Using conditional statements

If we run the script on a Thursday, we should see: “Today is Thursday”.

On days other than Thursday, we will see: “Today is not Thursday.”



?>


Basics of PHP

• PHP files end with .php

you may see .php3 .phtml .php4 as well • PHP code is contained within tags • <?php ?> or Short-open: <? ?> • HTML script tags: <script language="php"> </script>


Output

• Most things in PHP execute silently • You need to explicitly ask PHP to generate output • Echo is not a function and cannot return a value

– echo "<p>This is a paragraph.</p>";

• Print is a function and returns a value – 1 = success, 0 = failure– print ("<p>This is a paragraph too.</p>");

• Use echo or print statements and View Source for debugging your code


Variables

• All variables begin with $ and can contain letters, digits and underscore (and no digit directly after the $)

• The value of a variable is the value of its most recent assignment

• Don’t need to declare variables • Variables have no intrinsic type other than the type of

their current value • Can have variable variables $$variable

– Like a pointer variable type; best to avoid


Variables Scope• Scope refers to where within a script or program a

variable has meaning or a value • Mostly script variables are available to you anywhere

within your script. • Note that variables inside functions are local to that

function and a function cannot access script variables outside the function even if they are in the same file.

• The modifiers global and static allow function variables to be accessed outside the function or to hold their value between function calls respectively


Variable types

• Strings • Numbers

– Integers– doubles

• Booleans– TRUE / FALSE

• Arrays • Objects


Variable Examples• Integer$a = 1234; # decimal number$a = -123; # a negative number$a = 0123; # octal number (equivalent to 83 decimal)$a = 0x1A; # hexadecimal number (equivalent to 26 decimal)• Floating Point Numbers$a = 1.234; $a = 1.2e3; $a = 7E-10;• Boolean$foo = True; // assign the value TRUE to $foo

// == is an operator which returns a boolean if ($action == "show_version") { echo "The version is 1.23"; } // this is not necessary: if ($show_separators == TRUE) { echo "<hr>\n"; } // because you can simply type this: if ($show_separators) { echo "<hr>\n"; }


Variable Examples cont.• Strings (single or double quoted) echo 'this is a simple string'; echo 'You can also have embedded newlines in strings, like this way.'; echo 'Arnold once said: "I\'ll be back"'; // output: ... "I'll be back"echo 'Are you sure you want to delete C:\*.*?'; // output: ... delete C:\*.*?• Arrays$error_descriptions[E_ERROR] = "A fatal error has occured"; $error_descriptions[E_WARNING] = "PHP issued a warning";$error_descriptions[E_NOTICE] = "This is just an informal notice";

the last example is in fact the same as writing: $error_descriptions[1] = "A fatal error has occured";$error_descriptions[2] = "PHP issued a warning";$error_descriptions[8] = "This is just an informal notice";(The first method is useful if E_ERROR is defined as a constant etc).


Constants and Globals

To define a constant:define(“PI”, 3.1416);$area = PI*$radius*$$radius ;

Globals:◦ Defined outside any function; eg form variables…global $var1, $var2 ……function xyz() { $localvarX = $var1 …}


Arrays in PHP

• An array in PHP is actually an ordered map which maps values to keys. An array can be thought of in many ways. Each of the concepts below can be implemented in a PHP array, so you can choose which ever of these ideas that you understand to conceptualise an array.

• linearly indexed array • list (vector) • hashtable (which is an implementation of a map) • dictionary • collection • stack (LIFO) • queue (FIFO) • can easily simulate trees and linked lists with arrays

of arrays


Numerically-indexed arrays (Vector array)

Say that we have a list of marks out of 100 in a subject 95, 93, 56, 70, 65, 98◦ array value 1 - 95 ◦ array value 2 - 93 ◦ array value 3 - 56 ◦ array value 4 - 70 ◦ array value 5 - 65 ◦ array value 6 - 98

$marks = array (95, 93, 56, 70, 65, 98); generates a numerically-indexed array$marks[0] = 95 ;$marks[1] = 93 ;$marks[2] = 56 ;$marks[3] = 70 ;$marks[4] = 65 ;$marks[5] = 98 ;


Numerically-indexed arrays (cont)

The following code also generates a numerically-indexed array, allocating the next index after the highest current index to the element.◦ $marks[] = 95;◦ $marks[] = 93;

marks[0] is 95 and marks[1] is 93. Note that array indexes start at 0 by default.You can skip indices by allocating a specific index

to a value -◦ $marks[5] = 56;◦ $marks[] = 70;

will be allocate 70 to $marks[6].marks[5] is 56 and marks[6] is 70.


Associative arrays

• Say we have a list of marks out of 100 in a subject and we want to know who got what mark:• Adrian - 95, Matty - 93, Lance - 56, Stephen - 70,

Craig - 65, Andy - 98$marks = array ("Adrian"=>93, "Lance"=>56,

"Stephen"=>70, "Craig"=>65, "Andy"=>98);

• maps a value to a key • name is the key • mark is the value


List an associative array

list() in conjunction with each() assigns a key / value pair into the variables $key and $variable. The following code prints each key / value pair into a table. Note that $value might itself be an array.

reset($marks); // go to the beginning of the array echo "<table border=\"1\">"while (list($key, $value) = each($marks)) { echo

"<tr><td>$key</td><td>$value</td></tr>\n"; } echo "</table><hr>";


List an associative array (cont)

each() actually returns a array for each array item which includes the key and value as well as the index 0 mapped to the key and the index 1 mapped to the value. Reset() puts the index pointer back to 0. Hence if you are more comfortable with numeric indexes, you can do the following:

reset($marks); while ($row = each($marks)) { echo "Mark for $row[0] is $row[1]<br />"; }


Strings

Dot operator for concatenation (joining) singly quoted read in and store literally double quoted certain sequences beginning with \ are replaced

with special characters + \n \t \r \$ \" \\ Variable names are replaced with string

representations of their values Variable interpolation No limit on string length


String Functions

• boolean strcmp ($str1, $str2) • boolean strcasecmp ($str1, $str2) • boolean strstr ($str1, $str2) • boolean stristr ($str1, $str2) • int strlen($str) • string substr ($str, $start_pos, $len)


String functions (cont)

• string chop ($str) • string ltrim ($str) • string trim ($str) • string str_replace ($old_txt, $new_txt, $text) • string substr_replace ($old_txt, $new_txt, $text) • strtolower($str) • strtoupper($str) • ucfirst($str) • ucwords($str)


Formatting User Input/Output

• addslashes($str) • stripslashes($str) • escapeshellcmd($str) • strip_tags($str) • htmlspecialchars($str) • htmlentities($str) • nl2br($str) • …


Maths functions

• + - / * % • ++ -- • += -= *= • = is set to (assignment)• = = is equivalent to eg $a == $b Equal TRUE if $a is equal

to $b.• = = = is identical to eg $a === $b Identical TRUE if $a is

equal to $b, and they are of the same type. (PHP 4 only) • $low_int = floor ($double) • $high_int = ceil ($double) • $nearest_int = round ($double)

• (nearest even number if exactly .5) • $positive = abs ($number) • $min = min ($n1, $n2 … , $nn) • $max = max ($n1, $n2 … , $nn)


Control and flow

if (expr1) { } elseif (expr2) { } else { } while (cond) { } do { } while (cond) switch ($var) case a { } case b { } for ($i = 0; $i < expr; $i ++) { } foreach (array_expr as $value) { } foreach (array_expr as $key=>$value) { } breakcontinue


If.. Then.. else

* if ($a > $b) print "a is bigger than b";* if ($a > $b) { print "a is bigger than b"; $b = $a; }* if ($a > $b) { print "a is bigger than b"; } elseif ($a == $b) { print "a is equal to b"; } else { print "a is smaller than b"; }


While

/* example 1 */

$i = 1; while ($i <= 10) { print $i++; /* the printed value would be $i before the increment (post-increment) */ } /* example 2 - alternative notation to using the braces - : and endwhile*/ $i = 1; while ($i <= 10): print $i; $i++; endwhile;


For loops

/* example 1 similar to C syntax */ for ($i = 1; $i <= 10; $i++) { print $i; } /* example 2 */ for ($i = 1;;$i++) { if ($i > 10) { break;

} print $i;

} /* example 3 */ $i = 1; for (;;) { if ($i > 10) { break; } print $i; $i++; } /* example 4 */ for ($i = 1; $i <= 10; print $i, $i++);


Foreach

An easy way to iterate over arrays. There are two syntaxes; the second is a minor but useful extension of the first:

foreach(array_expression as $value) statement foreach(array_expression as $key => $value) statementThe following are functionally identical: //example 1 // reset ($arr); while (list(, $value) = each ($arr)) { echo "Value: $value<br>\n"; }//example 2 // foreach ($arr as $value) { echo "Value: $value<br>\n"; }


Foreach cont.

/* foreach example 1: value only */$a = array (1, 2, 3, 17); foreach ($a as $v) { print "Current value of \$a: $v.\n"; } /* foreach example 2: value (with key printed for illustration) */ $a = array (1, 2, 3, 17); $i = 0; /* for illustrative purposes only */ foreach($a as $v) { print "\$a[$i] => $v.\n"; $i++; } /* foreach example 3: key and value */ $a = array ( "one" => 1, "two" => 2, "three" => 3, "seventeen" => 17 ); foreach($a as $k => $v) { print "\$a[$k] => $v.\n"; }


Break & Continue

-break ends execution of the current for, foreach while, do..while or switch structure.

$arr = array ('one', 'two', 'three', 'four', 'stop', 'five'); while (list ($key, $val) = each ($arr)) { if ($val == 'stop') { break; /* You could also write 'break 1;' here. */ } echo "$val<br>\n";} /* note list() is a multiple assignment function; the key and value returned by each() are

assigned to $key and $value. $key is not used in this example.

-continue is used within looping structures to skip the rest of the current loop iteration and continue execution at the beginning of the next iteration.


Switch

if ($i == 0) { print "i equals 0"; }if ($i == 1) { print "i equals 1";}if ($i == 2) { print "i equals 2"; }/* this is equivalent */ switch ($i) { case 0:

print "i equals 0"; break; case 1: print "i equals 1"; break; case 2: print "i equals 2"; break; }


require() and include()

• require() includes and evaluates a specific file.• require() and include() are identical in every way except how

they handle failure. include() produces a Warning while require() results in a Fatal Error.

<?php require 'prepend.php'; require $somefile;require ('somefile.txt');?>

• require_once() or include_once() should be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, and you want to be sure that it is included exactly once to avoid problems with function redefinitions, variable value reassignments, etc.


What we covered today:

• Introduction To PHP• Variables, constants, arrays and strings• Control structures – sequence, repetition and

selection


Sources

• http://www.zend.com/zend/art/intro.php• http://www.php.net/• http://hotwired.lycos.com/webmonkey/

programming/php/index.html• www.phpbuilder.com


Next: More advanced PHP

modified from moseley ’s sli desweb applications development. lecture 5 slide 1 lecture 5:...

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