PHP Tutorial

Overview

Before You Start

This tutorial assumes:

• PHP 4.3.1 or greater is installed on your system. See Komodo's Installation Guide for configuration instructions.
• You are interested in PHP. You don't need previous knowledge of PHP; the tutorial will walk you through a simple program and suggest some resources for further information.

PHP Tutorial Scenario

This tutorial examines a PHP program that implements a form on a website - in this case, a guest book where site visitors can log comments. In addition to providing an overview and working example of PHP, the tutorial introduces Komodo's CGI Debugging functionality. In this tutorial you will:

1. Open the PHP Tutorial Project and associated files.
2. Analyze guestbook.php, the PHP program included in the PHP Tutorial Project.
3. Run the program and generate HTML output by running the program.
4. Debug the program using the Komodo debugger.

See Debugging Programs for more information on this Komodo functionality.

Opening the Tutorial Project

On the File menu, click Open|Project and select php_tutorial.kpf from the php_tutorials subdirectory. The location differs depending on your operating system.

Windows

<komodo-install-directory>\lib\support\samples\php_tutorials

Linux

<komodo-install-directory>/lib/support/samples/php_tutorials

Mac OS X

<User-home-directory>/Library/Application Support/Komodo/3.x/samples/php_tutorials

All files included in the tutorial project are displayed on the Projects tab in the Left Pane.

Overview of the Tutorial Files

The following components are included in the php_tutorial.kpf project file:

• guestbook.php: This PHP program writes data from an HTML form to a data file, then extracts the contents of the data file and formats it as HTML.

Open the PHP Tutorial File

On the Projects tab, double-click the file guestbook.php. The file opens in the Editor Pane; a tab at the top of the pane displays the filename.

Analyzing the PHP Tutorial File

This section reviews the code in guestbook.php.

Analyzing guestbook.php

Introduction

In this step, you will analyze the PHP program on a line-by-line basis. Ensure that line numbers are enabled in Komodo (View|View Line Numbers) and that the file guestbook.php is displayed in the Komodo editor.

HTML Header

Lines 1 to 8 - HTML Header

• a standard HTML header is written to the program output

PHP Declaration and Datafile

Line 9 - PHP Declaration

• PHP programs are embedded in HTML
• the characters <?php indicate the start of the PHP program

Lines 10 to 18 - Comments

• the // characters indicate a single-line comment in PHP programs; the # symbol can also be used. Multi-line comments are nested in /* and */ characters, as shown on lines 27 to 30

Line 22 - Datafile

• the file guestbook.dat is created if it does not exist
• the tmp directory must exist beneath the root of the drive where the program resides (unless a different location is specified in the Debugging Options).
• PHP statements are terminated with semicolons

GuestBook Class

Lines 25 to 28 - Class Declaration

• a class is a collection of variables and functions
• class GuestBook contains the functions GuestBook, _getData", outputData, etc
• the var statement declares variables as class members, thus making them portable across functions contained in the class

GuestBook Function

Lines 34 to 37 - GuestBook Function

• a function is a discrete block of code
• the $datafile argument is passed to the function GuestBook; multiple arguments are separated by commas
• the contents of a function are enclosed in braces
• $_SERVER is a pre-defined PHP variable; it is passed to the script from the web server
• • in PHP, global variables must be declared to be global inside a function if they are going to be used in that function
• a local variable is defined for the current function by use of the term $this; notice that the same syntax is used to call another function
• • gb_dat variable is declared on line 27
  • gb_dat variable is assigned the value of $datafile
  • $this->data variable is cleared of any prior value
  • $this->_getData variable calls the _getData function that begins on line 53; when the _getData function is complete, processing returns to line 40

Lines 40 to 44 - Check for Valid Form Entry

• if the REQUEST_METHOD contained in $_SERVER is equal to POST, processing passes to the addGuestBookEntry function on line 120
• if the REQUEST_METHOD is not equal to POST, a redirect message is displayed to the user
• • the echo command generates output
  • the characters \" are not included inside the double quotation marks that follow, so that the message can be displayed as output
  • the PHP variable PHP_SELF is the filename of the current script
  • $_SERVER["PHP_SELF"] extracts the PHP_SELF variable from the $_SERVER variable

Lines 45 to 46 - Check for Variable Value

• the if ($this->data) statement tests if the variable $this->data has a value
• • the program executes the outputData function and then the outputForm function

_getData Function

Lines 53 to 58 - _getData Function

• the "file" statement parses the contents of the file stored in the gb_dat variable into the $lines array
• • the @ symbol suppresses warnings; in this case, if the data file is empty, the program generates a non-fatal error
• the if ($lines) statement checks to see if the $lines variable has data
• the "join" statement converts the $lines array to a string and places it in the variable $this->data

outputData Function

Lines 64 to 66 - outputData Function

• the contents of the $this->data variable are written to the standard output using the echo statement

_createEntryHTML Function

Lines 72 to 77 - Retrieve Form Data

• the PHP variable $_POST is used to provide data to the script via HTTP POST
• lines 74 to 77 extract the form data and place the items in variables

Lines 80 to 83 - Validate Form Data

• On line 80, the validity of the name and message variables is tested:
• • in !$name and !$message, "!" is a "not" operator; it is true if either variable is not true
  • The || symbol is an "or" operator

Line 86 - Current Date and Time

• the variable $today contains the result of the PHP function date:
• • the date function returns a string
  • the "switches" are interpreted as follows:
  • • F: text month
    • j: numeric day within month
    • y: four digit year
    • g: hour (12 hour format)
    • a: AM / PM

Lines 89 to 94 - Interpolate Form Data with HTML

• text and HTML tags are parsed with the $today variable and the form data
• the return statement supplies the result (true or false) of a function or the value of a variable to the routine from which it was called

_writeDataFile Function

Lines 100 to 106 - Open the Data File

• the fopen function opens the file stored in the $this->gb_dat variable
• • the w switch opens the file if it exists
  • If the file does not exist, fopen will attempt to create it
  • the file is opened for writing only, and the file pointer is positioned at the top of the file
• the if !$f statement checks to see if the $f variable contains a value

Lines 108 to 110 - Write to the Data Files

• the fwrite function writes the contents of $this->data to the file contained in the $f variable

Lines 111 to 113 - Close the Data File

• the fclose function closes the file stored in the $f variable
• the value of the return statement is tested on line 112

addGuestBookEntry Function

Lines 120 to 125 - Call Functions for Writing Data

• the $entry variable is local to the addGuestBookEntry function
• the $entry contains the contents of the $data variable, returned in the _createEntryHTML function
• on line 123, the contents of $entry are concatenated with the contents of $this->data, and stored in $this->data

outputForm Function

Lines 127 to 142 - The Function for HTML Form

• these lines generate a standard HTML form
• notice the PHP snippet on line 133 that provides the program name to the HTML output

Closing Tags

Lines 148 to 151 - Closing Tags

• the $gb variable creates a new instance of the GuestBook class using the file specified in the $datafile variable
• when the functions in the GuestBook class are complete, the PHP program is closed using the syntax ?>
• closing HTML tags are written as output

Running the Program

This section reviews how to run the guestbook.php program using the Komodo debugger.

1. Run the debugger: Select Debug|Start.
2. Configure debugging options: In the Debugging Options dialog box, configure the following options:
3. • General tab: Select the Simulate CGI Environment check box.
   • CGI Input tab:
     • Set the Request Method option button to Post.
     • On the Post Type drop-down list, select URL encoded.
     • On the Type drop-down list, select the variable type Post.
     • Enter the following names in the Name text box, adding a meaningful value for each in the Value text box. For example, the value for "name" could be your own name. Click the Add button after each entry to add it to the Browser Arguments.
     • • "name"
       • "email"
       • "company"
       • "message"
4. Run the debugger: Click OK to run the debugger with the selected options.
5. View the Command Output tab: Notice the messages in the bottom left corner of the Komodo screen; these inform you of the status of the debugger.
6. View the rendered HTML: Click the HTML tab on the right side of the Debug tab. The HTML is displayed in the Bottom Pane; previous guestbook entries are displayed at the top of the output, and the HTML form is displayed at the bottom. Click the Output tab to return to the HTML code.
7. Create New File: To create a new HTML file that contains the HTML code on the Output tab, select File|New|New File. In the New File dialog box, select the Common Category, and the HTML template. Click Open.
8. Save the Output: Delete the contents of the new HTML file tab in the Editor Pane, then select the HTML code on the Output tab. Copy the contents to the new HTML file tab in the Editor Pane using the key binding associated with your selected scheme. Select File|Save As to save the file with a unique name.

Debugging the Program

In this step you will add breakpoints to the program and debug it. Adding breakpoints lets you run the program in chunks, making it possible to watch variables and view output as it is generated. Before beginning, ensure that line numbering is enabled in Komodo (View|View Line Numbers).

1. Set breakpoints: On the guestbook.php tab in the editor, click on the gray margin immediately to the left of the code in line 9 of the program. This sets a breakpoint, indicated by a red circle. Set a second breakpoint on line 148.
2. Run the debugger: Select Go|Continue. In the Debugging Options dialog box, click OK to accept the defaults (assuming that you created the CGI variables in the previous step, Running the Program).

3. Watch the debug process: A yellow arrow on the breakpoint indicates the position at which the debugger has halted.
4. Line 9: Step In: Select Debug|Step In. "Step In" is a debugger command that causes the debugger to execute the current line and then stop at the next processing line (line 19). The lines between line 9 and line 19 are comments, not processing statements, and are therefore ignored by the debugger.
5. View Variables: Expand the Bottom Pane (if necessary) by clicking and dragging the bottom margin of the Komodo workspace. Variables defined in the program are displayed on the Locals tab.
6. Line 19: Select Go|Continue. The debugger moves to line 148. The GuestBook class is called from line 148.
7. Line 148: Step In: The debugger is now processing the GuestBook function.
8. View Variables: The Locals tab displays all variables.
9. Line 35: Step In: Expand the $this variable on the Locals tab in the Bottom Pane. Notice that it now has a sub-variable gb_dat, which stores the value of the data file.
10. Line 36: Step In: Continue to step in until the debugger stops at the _getData function. Continue to select Step In to process each statement in the function. After line 57 has been processed and the debugger is stopped at line 58, the $lines variable can be expanded on the Locals tab.
11. Line 58: Step Out: On line 58, select Step Out to process the rest of the _getData function. The debugger will proceed to line 40, which follows the line where _getData was called.

14. Line 40: Step In: Continue to select Step In until the debugger is on line 121, in the addGuestBookEntry function. On line 121, the addGuestBookEntry function calls the _createEntryHTML function.
15. Line 121: Step In: In the _createEntryHTML function, the program assigns variables to the CGI input data configured in the Debugging Options.
16. Line 74: Step Out: The _createEntryHTML function completes, and processing returns to line 122.
17. Line 122: Step In: Use Step In to process each line of the addGuestBookEntry function, until processing moves to the _writeDataFile function on line 102.
18. Line 102: Step In: Process line 102.
19. Open Watch Window: On line 102, the program opened the datafile (by default, \tmp\guestbook.dat). To watch the activity in the datafile, select Tools|Watch File, then specify the datafile.
20. Line 103: Step In: Continue to select Step In until line 108 has been processed. After line 108 is processed, the contents of the $this->data variable are written to the datafile, as displayed in the Watch tab.
21. Line 111: Step In: Step In until processing returns to line 45 of the GuestBook function.
22. Line 45: Step Over: The Step Over debugger command executes the current line, including any functions called by the current line. When the debugger returns to line 46, notice that the contents of the $this->data variable have been written to the Bottom Pane.
23. Line 46: Step Over: The debugger executes the outputForm function, which writes the HTML form to the Bottom Pane.
24. Continue: Select Debug|Continue to run the debugger to the end of the program.

More PHP Resources

ASPN, the ActiveState Programmer Network

ASPN, the ActiveState Programmer Network, provides resources for PHP programmers:

• Mailing lists with many PHP topics.

Tutorials and Reference Sites

There are many PHP tutorials and beginner PHP sites on the Internet, including:

• The PHP Resource Index, a collection of resources dealing with PHP.
• www.PHP.net, the home of all that is PHP-related.