Debugging PHP in Zend Studio

This tutorial will teach you how to debug files and applications to gain maximum efficiency and accuracy from your PHP code.

Zend Studio 's Debugging feature can detect and diagnose errors in PHP code situated locally or on remote servers. The debugger allows you to control the execution of your program by setting breakpoints, suspending launched programs, stepping through your code, and examining the contents of variables.

Debugging should be used at stages where your scripts and applications are formed sufficiently to be tried and tested.

Tutorial Content

In this tutorial, you will learn:

To create a new local PHP project
To create a new PHP file
To set breakpoints
To debug a PHP file as CLI
To debug a PHP file as a Web application

Provided Items

Throughout the tutorial, you will be provided with code snippets to insert in your project.

Prerequisites

Zend Studio 12.0 or above which can be downloaded from the Zend Studio Downloads page. For information on installation, see the Zend Studio Installation Guide.
Zend Studio debugs using the Zend Debugger. If you would like to debug using the Xdebug extension, see Installing Xdebug and Configuring Zend Studio for Debugging with Xdebug

Related Media

To better understand the procedures described in this tutorial, watch this video:

Step 2: Creating a New PHP File

Next, we will begin to develop our application by adding a new PHP file to the project.

Instructions on how to complete a procedure

To create a new PHP file:

In the PHP Explorer view, select the newly created project.
Right-click, and select New | PHP File.
The PHP File creation dialog is displayed.

Name the new file 'debug.php', and click Finish.
The new file is added, and displayed in the PHP Editor and PHP Explorer views.
Paste the following example code into the new file:

<HTML>
<BODY>
<H1>Debug Demo</H1>
<table border="1" width="700">
	<tr bgcolor="red">
		<th>Name</th>
		<th>Address</th>
		<th>Phone</th>
	</tr>
<?php
	$db = array(
	array ("John", "E 10th St., NYC, NY 23742", "(212) 555-4456"),
	array ("Francois", "12 Bd. de Grenelle, Paris, 74897","(33) 433-544"),
	array ("Klaus", "312 Beethoven St., Frankfurt, Germany", "(44) 332-8065"),
	array ("Shirly", "72 Independence St., Tel Aviv, Israel 67283", "(972) 156-7777"),
	array ("Bill", "127 Maine St., San Francisco, CA 90298", "(415) 555-6565")
	);
/**
@return string
@param i int
@desc Returns 'white' for even numbers and 'yellow' for odd numbers
*/
function row_color($i)
	{
	$bgcolor1 = "white";
      	$bgcolor2 = "yellow";
	if ( ($i % 2) == 0 ) {
		return $bgcolor1;
		} else {
		return $bgcolor2;
      		}
	}
/**
@return void
@desc Displays a table of the workers
*/
function display_workers()
	{
	global $db;
	for ($i=0 ; $i < count($db); $i++) {
		$worker_data = $db[$i];					
		$worker_name = $worker_data[0];
		$worker_address = $worker_data[1];
		$worker_phone = $worker_data[2];
		print "<tr bgcolor=\"".row_color($i)."\">\n";
		print "<td>$worker_name</td>\n";
		print "<td>$worker_address</td>\n";
		print "<td>$worker_phone</td>\n";
		print "</tr>\n";
		}
	}
	display_workers();	
	echo $undefined_variable;
?>
</table>
</BODY>
</HTML>

Save the file.

Step 3: Setting Breakpoints

By default, Zend Studio is configured to stop debugging at the first PHP line in the code. Our next step is to add an additional breakpoint to specify where in the code the debugging process should pause.

Instructions on how to complete a procedure

To add breakpoints in your code:

In the new 'debug.php' file, locate line 37.
Double-click the vertical ruler to the left of the line.
-OR-
Select the line, and go to Run | Toggle Breakpoint.
-OR-
Press Ctrl+Shift+B.
A blue ball will appear, indicating that a breakpoint has been set.

Save the file.

To learn how to add conditions to a breakpoint, see Setting Breakpoints.

Step 4: Debugging as a CLI Application

We will now debug the file as a CLI application using Zend Studio's internal debugger.

Instructions on how to complete a procedure

To debug the file as a CLI application:

Right-click the file in the PHP Explorer, and select Debug As | CLI Application.
Click Yes if asked whether to open the PHP Debug Perspective.
A number of views will open with information about your script, and the debugging process stops where your first <?php label appears.

The Debug View (1) is where the debug stack trace is displayed and the debugging process can be monitored and controlled.

In the toolbar, click the Resume icon to continue to the set breakpoint.
In the toolbar, click the Step Into icon .
The Debugger goes into the display_workers function, and advances to line 52.
The Variables view (3) will now display various information about the relevant variables and parameters through which the function was reached.
The Debug Output view will display the HTML output created up until the breakpoint, while the Browser Output view will show the current output to a browser.

In the Debug view, click Resume until the debugging process is terminated.
Notice that as the debugging process progresses, the Debug Output and Browser Output displays are updated.
The console view will display any errors or warnings about your script. In this case, it will display a Notice about an undefined variable on line 53.

In the top-right corner of the perspective, click on the PHP Perspective icon to return to normal editing mode.

To run the debugging process again with the same configuration, click the debug icon on the toolbar.

To change debugging configurations, in the menu-bar, go to Run | Debug Configurations.

Step 5: Debugging as a PHP Application

Zend Studio also allows you to debug applications, projects or files that are located on a server. You can debug either the local (Workspace) copy of files or the server copy of files.

Instructions on how to complete a procedure

To debug as a Web application:

Place your application on a Web server.

Right-click the file in the PHP Explorer, and select Debug As | PHP Web Application.
The Debug PHP Web Application is displayed.

Make sure the URL is correct, and modify it if needed.
Click OK.
Click Yes if asked whether to open the PHP Debug Perspective.
A number of views will open with information about your script, and the debugging process stops where your first <?php label appears.

Select the Browser view (tabbed with the Editor view).
This view shows the output of the script to the browser. This will be updated as the debugging process continues. For now though, it will be empty.
In the toolbar, click the Resume icon to continue the debugging.
The debugger stops at the set breakpoint on line 37.
Click the Resume icon again.
The debugging is terminated, and the Browser view displays the output of the file.

To run the debugging process again with the same configuration, click the debug icon on the toolbar.

To change debugging configurations, in the menu-bar, go to Run | Debug Configurations.