FIT3084: PHP : Hypertext Processor

In the previous lecture:

• Reduce image file sizes with an appropriate compression scheme.
• Use an appropriate file format (e.g. bitmap (GIF, JPEG, PNG) or SVG) to avoid image artefacts.
• Use tricks like interlacing, thumbnails, ALT, WIDTH and HEIGHT attributes to improve the user experience of your image content.

In this lecture:

• PHP syntax
• PHP examples

References

Sebasta, R.W., "Programming the WWW 2009", 5th edition, Pearson, chapter 9.

http://www.php.net/

About A server-side scripting language. Often used for form handling and WWW database access. An alternative to CGI, ASP, ASP.NET and JSP. An Open Source project so we will discuss it rather than ASP and JSP. The brainchild of Rasmus Lerdof (1994). An acronym (originally) for Personal Home Page (tools) but now PHP: Hypertext Processor.

How does PHP work? PHP code is embedded in XHTML documents (like JavaScript) PHP is interpretted by the server (unlike JavaScript... it is not seen by the client) A server recognises a request for an XHTML document that contains PHP (often identified by file extension .php, .php3 or .phtml). The PHP processor is called to interpret the code. The processor sees XHTML (or JavaScript) in the file and copies it directly to the output file to send to the client. The processor sees PHP in the file and executes it to create XHTML source or embedded client-side scripts and copies this to the output file to send to the client. The result is always that XHTML (possibly with embedded client-side scripts) is sent back to the client that made the request. So... If a surfer does "view source" on a page that contained PHP... they will not see the PHP source.

The PHP Language

PHP syntax is very similar to that of JavaScript and in some ways Perl. We shall only discuss it briefly...

Terminate PHP statements with a semicolon ;

Including PHP in an XHTML document

• Embed source between <?php and ?> tags in the XHTML document that requires it.
  
  
• Or write PHP into a separate file from the XHTML and include it using: include ("myPHPfile.inc");
  The included file can contain XHTML, JavaScript and PHP source but the PHP must appear within this file between <?php and ?> tags even if the include( ) was already between such tags.
  
  
• On some servers the first line of a file containing PHP must be a path to the interpretter (e.g. #!/usr/local/bin/php)
  

PHP comments

# Perl style comment
// C++ style single-line comment
/* and */ C style multi-line comment

PHP Variables

• All variables begin with the $ symbol
• Variable names are case sensitive
  
  
• An unassigned variable has the special value NULL
  If a variable with value NULL is used in an expression, its value is "coerced" into the necessary type (e.g. 0 or the empty string)
  Test whether a variable has been assigned to: IsSet($myVariable) == TRUE

PHP basic types

• PHP is dynamically typed.
• Type is set at each assignment to a variable (Hence, NULL is actually a PHP variable type).
• There is no way (or need) to directly declare the type of a variable.

Four scalar types:

1. Boolean (TRUE and FALSE case insensitive)
2. integer (actually a long integer)
3. double
4. string

Operators and expressions for numeric types

Useful functions that operate on integers and doubles include:

PHP string manipulation and printing

This 'string' and this "string" are both valid but...

The delimiters ' and ' ensure that embedded variables and escape sequences are not interpretted.

So assuming: $fred = 2; $tom=3; then

Source code	Output
print 'The value $fred.\nThe value $tom.';	The value $fred.\nThe value $tom.
print "The value $fred.\nThe value $tom.";	The value 2. The value 3.
print "0.8 \$USD = 1.0 \$AUD";	0.8 $USD = 1.0 $AUD

Operators and expressions for Strings

String concatenation: $beforeButterfly = "cat" . "er" . "pillar";

Accessing characters in a string: $beforeButterfly{2} has the value "t"

Useful functions for string manipulation include the usual ones and a lot more.

More PHP Output

The output from a PHP script must be XHTML or client-side script source code that will form part of the XHTML document containing the code.

print "This is a line of text<br /> and this is another.";

print "49"; and print(49); will both print out 49

print does not require the brackets ( and ).

printf("The value is %d", $fred);

printf( ) makes available all of the standard C printf( ) output formatting codes.

printf( ) requires the brackets ( and ).

PHP allows file I/O to files anywhere on the internet (and the server) using HTTP and FTP protocols. Consult (for example) http://au.php.net/manual/en/features.remote-files.php for details.

Control Structures

The relational and boolean operators >, <, >=, <=, !=, == all work as expected.

!, &&, || as well as and, or, xor are available too.
and and or have lower precedence than && and || but are otherwise the same.

=== is TRUE iff both operands are of the same type and exactly the same value (and conversely !== ).

If the types of operands compared using > < >= <= != == are not the same, one is coerced into the other's type. Be careful about this!

Selection and Iteration statements:

if ( ... )
{ ... }

elseif ( ... )
{ ... }

else
{ ... }

switch ($variableName)
{

while ( ... )
{
 ...
}

for (...; ...; ...)
{
 ...
}

do
{
 ...
} while ( ... );

break and continue work as in C.

Sample PHP Script : Calculation

This computes the average of a random number of random values between 1 and 1000.

#!/usr/local/bin/php

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Simple PHP Script</title>
</head>

<body>
<p>This is a simple page to display the result of a simple calculation performed in PHP.</p>
<p>

<?php
         srand(time());
         $numberOfValues = rand(1,100);
         $totalRatings = 0;

         for ($i=0; $i<$numberOfValues; $i++)
         {
             $total_ratings += rand(1,1000);
         }

         $average = $totalRatings / $numberOfValues;
         print("The average random value of $numberOfValues values between 1 and 1000 is: $average");
?>

</p>
</body>
</html>

Average random value script

PHP Arrays

PHP arrays are conventional non-negative integer-accessed arrays, hashes, or a mixture of both!

Array elements contain a value and a key.

The key may be a non-negative integer (standard array style ordered 0...n) or a string (hash style).

The values stored in an array may be of different types.

Creating and filling arrays

Accessing array elements

Sequential array access

$todayTemperature = $temperatureArray["Wednesday"];
print "Today's temperature will be $todayTemperature degrees.";

$names = array("Alan", "Marco", "Mario", "MC Spandex");
$length = sizeof($names");

$ageArray = array("Alan"=>30, "Marco"=>33, "Mario"=>31, "MC Spandex"=>27);
       
while($rider = each ($ageArray))
{
   $name = $rider["key"];
   $age = $rider["value"];
   print("The age of $name is $age <br />");
}

foreach ($ageArray as $age)
{
   print ("$age <br />");
}

foreach ($ageArray as $name => $age)
{
   print("The age of $name is $age <br />");
}

PHP Functions

function name ([optional parameters])
{ ... }

function capValue( &$valueToCap )
{
   if ($valueToCap > 100)
   { $valueToCap = 100; }
}

Sample PHP Script : Form Handling

• Define the form source in one XHTML document.
• Define the PHP form processing software in another XHTML document.
• Specify the name of the form processing software file in the form source file using its <form> tag's action attribute.
• Access the form source's data within the form processing software file from the hash $_POST or $_GET depending on the form's method attribute.

<body>
<h2>Official Certificate of Super Stardom</h2>
<p>By the authority vested in me, the lecturer, I hereby declare that

<?php
       $givenName = $_POST["givenName"];
       $familyName = $_POST["familyName"];
       print " $givenName $familyName is";

if ($_POST["superstarBox"] == FALSE)
{ print " <strong>not</strong>"; }

print " a superstar. <br />";
print "In addition, it is hereby officially recognised that";

if ($_POST["gender"] == male)
{ 	$pronoun = "he"; $possessivePronoun = "his"; }
       
else
{  $pronoun = "she"; $possessivePronoun = "her"; }
       
switch($_POST["loveHate"])
{
       case "love": $who = "everybody"; break;
       case "hate": $who = "nobody"; break;
       default: $who = "only $possessivePronoun Mum";
}
   
print " $pronoun is a person whom $who loves."
?>

</p>
<p>Signed, <br /> The Lecturer.</p>
</body>

....Phew! There is still more to know about PHP but that just about covers the basics.

• PHP looks very much like a lot of other programming languages.
• PHP scripts are embedded or included in XHTML documents (like JavaScript).
• PHP is not interpretted by the client/browser, but on the server.
• The client never sees any PHP source code, only the XHTML it exports.
• PHP makes form handling very simple.

Courseware | Lecture notes

©Copyright Alan Dorin 2009