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IT 280 Web Development II, Spring 2008

Dynamic pages with PHP - part 1

PHP is a server-parsed language. It is processd by the http server program before the page is returned to the browser.
The name "PHP" is a recursive acronym that stands for "PHP: Hypertext Preprocessor".
PHP is available on many platforms (Linux or Unix with Apache, Windows with Apache or IIS).
PHP is a complete programming language that has many powerful functions.
Some of the functions and language features are especially designed for the Web environment.

PHP Blocks

PHP statements are incorporated into an HTML document using special tags and are interpreted by the server before the document is returned to the browser.
PHP lets you put many statements together inside a single tag called a block.
Each statement within a block must end with a semicolon.
A PHP block in a document starts with .
A PHP block can be placed anywhere in the document.
When the document is requested, the program statements in the block are executed and the entire block is replaced with the result.

Comments

Single-line comments in PHP begin with //.
Everything from the // to the end of the line is comment.
You can also use multi-line comments delimited by /* and */.
As with all programming, you should include appropriate comments in your code.

Example:

<?php 
      //This is a comment.  It is for the programmer to read.
      /*This is another comment.
        It could provide a longer explanation
        of the program for the reader 
        
        This form of comment is also useful if
        you text editor tends to break long lines 
        without warning you 
      */
 ?>

The `echo` command

The echo command inserts output into the returned document.
It is similar to rthe JavaScript document.write
Its arguments can be expressions using strings, numbers, operators, and variables.
Multiple arguments are separated by commas.
You can have line breaks inside a quoted string literal.

Example:

<?php
		echo "Hello there!";  // A basic statement 		
	
		echo "2 + 3 = ", 2 + 3;   // Two arguments separated by a comma.
		  		
		echo "This quoted source text
		spreads across
		more than one line.";
?>

Publishing PHP documents

PHP documents must be stored in the web documents directory (your WWW directory)
File extension: PHP documents must have the extension .php.
If the file does not have the correct extension, the PHP statements will not be interpreted.

Example 1:

<html>
 <head>
  <title>PHP Example One</title>
 </head>
 <body>

  <h1>This is the first PHP example</h1>
<?php
		echo "Hello there!"; // A basic statement 		
	
		echo "2 + 3 = ", 2 + 3; // Two arguments separated by a comma.
		  		
		echo "This source text
		spreads across
		more than one line.";
?>  		
</body>
</html>

The example directory for the first example contains the example as

first.txt: plain text - you see all the code as written.
first.htm: HTML - the PHP commands are treated as comments
first.php: server-parsed file - the PHP commands are executed and you get only the results.

Variables

Variables in PHP are written with a dollar sign followed by the name of the variable.
Variable names are case-sensitive.
A variable name must begin with a letter or underscore, followed by any number of letters, numbers, or underscores.
Variables are assigned values using the = operator.

Example:

<?php
  $aa = "Hello ";
  $bb = "world! ";
  echo $aa, $bb;
  $xx = 12;
  $yy = 10;
  echo $xx * $yy;
?>

The example directory for the second example contains the example as

second.txt: plain text - you see all the code as written.
second.php: server-parsed file - the PHP commands are executed and you get only the results.

Predefined variables

PHP provides a large number of predefined variables.
Many of these variables depend upon which server is running, the version and setup of the server, and other factors.
Some of the predefined variables provide access to the values that are shown by the phpinfo() function discussed last week.
- Their names are indicated in the table headed PHP Variables near the end of the page.
- Most of the names begin with an underscore. It is part of the name.
- Many variables have the same basic name followed by a string in square brackets. The brackets and string are part of the name.
Warning: the phpinfo() output only shows the name part; You must prepend the $.

Example:

<h1>This is the third PHP example</h1>

<?php  echo $_SERVER["QUERY_STRING"]; ?>

<!-- This part is in the HTML, not inside a PHP block -->
<!-- So these are HTML comment elements. -->
<br />
<!-- break tag for a more readable page. -->

<?php
	// We can print the break from inside a PHP block
	// In here we must use PHP Comments
    echo $_SERVER["REMOTE_ADDR"], "<br />";
?> 

<?php
    echo $_SERVER["REQUEST_URI"], "<br />"; 
    echo $_SERVER["PATH_TRANSLATED"]; 
 ?>

The example directory for the third example contains the example as

third.txt: plain text - you see all the code as written.
third.php: server-parsed file - the PHP commands are executed and you get only the results.

Activity

First request the third.php example
Then edit the URL in the browser's location bar so it requests third.php?Hello_World!.

The `include` function

The PHP function include

should have the name of the included file following the command
- the file name is a string
- it can be a literal (in quotes) or a variable
tells the server to:
1. get the specified file
2. process it like another .php file (no matter what its extension)
3. insert the results into the final document.

The name of the included file is written following the command.

Example:

<html>
<!--  The file fourth.php -->
<head><title>fourth PHP page</title</head>
<body>

<h1>Fourth PHP Example - using include</h1>

<?php include "included.txt"; ?>

<p>Notice that even though the included file has the extension .txt, the PHP commands in it are processed.</p>
</body>
</html>

<!--  The file included.txt -->
<p>The following line comes from the included file.</p>

<h2><?php
  echo 2 + 3 * 5 ?></h2>

The example directory for the fourth example contains

the example as fourth.txt: plain text - you see all the code as written.
the example as fourth.php: server-parsed file - the PHP commands are executed and you get only the results.
the included.txt: the included file.

The PHP date function

The PHP date() function will return the current date and time in a variety of formats.
Its argument should be a string that includes codes for the formats.

A few of the many possible codes are

d   Day of the month as 2 digits with leading zeros   01 to 31
D   Day of the week as three letters                  Mon through Sun
l   Full name of the day of the week (lowercase 'L')	Sunday through Saturday
M   Name of the month as three letters                Jan through Dec
F   Full name of the month                            January through December
Y   Numeric representation of a year as 4 digits      Examples: 1999 or 2005

There can be other characters in the string. If they are not codes, they will be unchanged.
If you want to include a character literally but it is a code, you must precede it with a backslash.
For more information about the function, including a complete list of codes, see the documentation on it.

Example:

<?php
  echo "Today is ";
  echo date ("l, F d, Y"); 
?>

In this example, we did not place the "Today is" inside the date argument string because the phrase contains letters such as d and y that would have been interpreted as codes.

Alternatively, we could have escaped the characters. However there are so many codes that we would have to escape every letter!

<?php
  echo date ("\T\o\d\a\y \i\s l, F d, Y"); 
?>

The example directory for the fifth example contains

the example as fifth.txt: plain text - you see all the code as written.
the example as fifth.php: server-parsed file - the PHP commands are executed and you get only the results.
the fifth_x.php: a version with the characters "Today is" inside the argument string.
the fifth_z.php: a version with the escaped characters "\T\o\d\a\y \i\s" inside the argument string.

Conditional statements

PHP has a conditional if..elseif..else statement.
The condition must be enclosed in parentheses.
The basic operators are the same as in JavaScript and several other languages. In particular, == tests for equality.

Example:

<?php
  $x = date("D");
 
  if ($x == "Fri") 
    {
   echo "It's Friday!!!! "; 
   echo "Have a great weekend!";
    }
  else
    {
    echo "Have a nice day.";
    echo "<br />Try me again on Friday!";
    }
?>

The example directory for the sixth example contains

the example as sixth.txt: plain text - you see all the code as written.
the example as sixth.php: server-parsed file - the PHP commands are executed and you get only the results.

Exercise Lab 09

For this exercise, you will create a basic PHP document. It should:

Include your name in PHP comments.
Display (echo) the text "This is a PHP page." The line should be a level 1 heading.
Assign the values 13 and 89 to variables $alphy and $bety
Display the sum and product f the variables, with appropriate text.
include a file named morestuf.txt. The included file should have PHP commands to display a list with
- the identity (PHP_SELF) of the document that is being executed.
- the date in the format YYYY/MM/DD (4-digit year, 2-digit month and day)
- the request's QUERY_STRING, HTTP_USER_AGENT, REMOTE_ADDR, and REQUEST_METHOD

Be sure to add the lab to your table of contents page and to complete the entry on Blackboard.

Comments to: chang@hood.edu

Last Modified: 11 May 2008. 20:24

IT 280 Web Development II, Spring 2008

Dynamic pages with PHP - part 1

PHP Blocks

Comments

The echo command

Example:

Publishing PHP documents

Example 1:

Variables

Example:

Predefined variables

Example:

Activity

The include function

Example:

The PHP date function

Example:

Conditional statements

Example:

Exercise Lab 09

The `echo` command

The `include` function