PHP Tutorial

(Komodo IDE only)

Overview

Before you begin

This tutorial assumes:

PHP 4.4 or greater is installed on your system. See the Debugging PHP documentation for installation and 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:

Open the PHP Tutorial Project and associated files.
Analyzing the PHP Tutorial File, the PHP program included in the PHP Tutorial Project.
Run the program and generate HTML output by running the program.
Debug the program using the Komodo debugger.

See Debugging Programs for more information on this Komodo functionality.

Opening the Tutorial Project

Select Help > Tutorials > PHP Tutorial.

The tutorial project opens and is displayed in the Places sidebar.

Overview of the Tutorial Files

The following components are included in the PHP Tutorial 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

In the Places sidebar, double-click the guestbook.php file. The file opens in the Editor Pane, and a tab at the top of the pane displays the filename.

Analyzing the PHP Tutorial File

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

Tip: Syntax elements are displayed in different colors. You can adjust the display options for language elements in the Preferences dialog box.

PHP Declaration and Datafile

Line 9 - PHP Declaration

PHP programs are embedded in HTML
<?php indicates 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 guestbook.dat file 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 Preferences page).
PHP statements are terminated with semicolons.

Tip: On line 23, type $da. Komodo displays a list of the variables declared above the cursor position that begin with the letters da. This is AutoComplete.

GuestBook Class

Lines 25 to 28 - Class Declaration

A class is a collection of variables and functions.
The GuestBook class 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.

Tip: Click the mouse pointer at the end of line 25. Notice that the brace changes to a bold red font. The closing brace on line 144 is displayed the same way. In this case, the braces mark the beginning and end of a class. See Editing Files for more information about matching braces.

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

Tip: On line 38, type function GuestBook(. When you type the left parenthesis, Komodo displays a pop-up hint that describes parameters for the function GuestBook. This is a CallTip.

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.

Tip: Use the “@” operator with care, otherwise you could disable error messages for critical errors that terminate the execution of the script.

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

PHP Pointer: PHP has two “or” operators: the word “or”, and the symbol ||. The || operator has precedence over the word “or”, providing flexibility in logic tests.

Line 86 - Current Date and Time

The $today variable 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

Tip: Click on the minus symbol to the left of line 100. The entire_writeDataFile function collapses. This is Code Folding.

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.

Run the debugger: Select Debug > Go/Continue.
Configure debugging options: In the Debugging Options dialog box, configure the following options:
- General tab:
  - Select the Use the CGI interpreter (php-cgi or php) check box.
  - 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
Run the debugger: Click OK to run the debugger with the selected options.
View the Command Output tab: Notice the messages in the bottom left corner of the Komodo screen that inform you of the status of the debugger.
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.
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.
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).

Tip: Debugger commands can be accessed from the Debug menu, by shortcut keys, or from the Debug Toolbar.

Step In: Executes the current line of code and pauses at the following line.
Step Over: Executes the current line of code. If the line of code calls a function or method, the function or method is executed in the background and the debugger pauses at the line that follows the original line.
Step Out: Executes the code without stepping through the code line by line (when the debugger is within a function or method). The debugger stops on the line of code following the function or method call in the calling program.

For a summary of debugger commands, see Debugger Command Description.

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.
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). The Debugger Options have been saved from the last time a PHP program was run or debugged.
Watch the debug process: A yellow arrow on the breakpoint indicates the position at which the debugger has halted.
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.
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.
Line 19: Select Go > Continue. The debugger moves to line 148. The GuestBook class is called from line 148.
Line 148: Step In: The debugger is now processing the GuestBook function.
View Variables: The Locals tab displays all variables.
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.
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.
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.
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.
Line 121: Step In: In the _createEntryHTML function, the program assigns variables to the CGI input data configured in the Debugging Options.
Line 74: Step Out: The _createEntryHTML function completes, and processing returns to line 122.
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.
Line 102: Step In: Process line 102.
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.
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.
Line 111: Step In: Step In until processing returns to line 45 of the GuestBook function.
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.
Line 46: Step Over: The debugger executes the outputForm function, which writes the HTML form to the Bottom Pane.
Continue: Select Debug > Continue to run the debugger to the end of the program.

More PHP Resources

Tutorials and Reference Sites

There are many PHP tutorials and beginner PHP sites on the Internet, including www.PHP.net, the home of all that is PHP-related.