Everyone knows that code debugging is very important during the development process. Debugging skills for some common errors can help improve the efficiency of code writing.
This article describes various ways to debug PHP applications, including turning on error reporting in Apache and PHP, and finding the source of more difficult bugs by strategically placing print statements in a simple PHP script. . You'll also learn about the PHPEclipse plug-in for Eclipse, a flexible development environment with real-time syntax parsing capabilities, and the DBG debugger extension for PHPEclipse. Introduction There are many PHP debugging techniques that can save a lot of time when coding. An effective yet basic debugging technique is to turn on error reporting. Another, slightly more advanced technique involves using print statements, which can help pinpoint harder-to-find bugs by displaying what actually appears on the screen. PHPEclipse is an Eclipse plug-in that highlights common syntax errors and can be used in conjunction with the debugger to set breakpoints.
Setup To learn the concepts described in this article, PHP, a web server, and Eclipse are required. The debugger extension supports PHP version V5.0.3. We need a web server to parse pages created with PHP and display them to the browser. Apache2 is used in this article. However, any web server will suffice. To take advantage of some of the debugging techniques introduced in this article, you need to install Eclipse V3.1.1 and the plug-in PHPEclipse V1.1.8. Since Eclipse requires Java™ technology, download it as well. Also requires PHP debugger extension module. Installing it is a little tricky. Please follow the instructions for installing the debugger extension carefully. Now, comment out the lines in the php.ini file that require the PHP extension to be loaded and configured. Uncomment it when you need to use the debugger. Please see Resources for download information. Now about the error messages.
Error message Error message is the first line of defense as a developer. No one wants to develop code in PHP on a server that is not configured to display error messages. However, please remember that when you have debugged your code and are ready to run it, you should make sure that error reporting is turned off as you do not want your site visitors to see error messages as this will give them enough information to exploit the site's weaknesses and Hack the site. You can also use error messages to your advantage, since they show the correct line of code that threw or generated the error. This way, debugging becomes a matter of looking in the browser at the line number where the generated error appears and inspecting that line in the code. Later, you'll see that the PHPEclipse plug-in can be of great assistance during development and debugging by underlining syntax errors on the fly and marking syntax errors with a red "x" when saving the file. Let’s first look at how to enable error reporting and set the level of error reporting in the php.ini file. You'll then learn how to override these settings in Apache's configuration files. Error reporting for PHP There are many configuration settings in the php.ini file. You should already have your php.ini file set up and placed in the appropriate directory, as documented in the instructions for installing PHP and Apache 2 on Linux (see Resources). There are two configuration variables that you should be aware of when debugging PHP applications. Here are the two variables and their default values:
Copy code The code is as follows:
display_errors = Off
error_reporting = E_ALL
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You can find it by searching for them in the php.ini file The current default values of these two variables. The purpose of the display_errors variable is obvious - it tells PHP whether to display errors. The default value is Off. However, to make the development process easier, set this value to On:
Copy code The code is as follows:
display_errors = On
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error_reporting variable The default value is E_ALL. This setting will show everything from bad coding practices to harmless tips to errors. E_ALL is a bit too granular for development purposes, as it also displays hints on the screen for small things (such as variables not being initialized), which messes up the browser's output. I only want to see errors and bad coding practices, but not harmless tips. So, please replace the default value of error_reporting with the following value:
<?php
$j = "";
print("Lets retrieve all the variables submitted to this ");
print("script via a GET request:<br>");
foreach($_GET as $key => $i){
print("$key=$j<br>");
}
if($_GET['Submit'] == "Send GET Request")
$j = "done!<br>";
?>
<form method="GET">
Name: <input name="name"><br>
Email: <input name="email" size="25"><br>
<input name="Submit" type="submit" value="Send GET Request">
</form>
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您可能会非常容易地发现清单 2 中的 bug！您很棒！但请注意这是一个非常简单的脚本，只是作为使用 print 语句进行调试而展示的一个例子而已。这个脚本只是提取 GET 请求中的所有变量，如果有，就把它们显示在浏览器上。还提供了一个表单，用 GET 请求向服务器发送变量以进行测试。请看输出，如图 2 所示。 图 2. test2.php 的输出
对于本文中使用的插件和扩展的版本，断点功能是必需的，因为 PHP 在把输出发送到浏览器之前会缓冲它。除此之外，需要做的不仅仅是设置一个断点把当前显示数据刷新到 Web 浏览器，所以要像下面和图 8 所示那样定义 test4.php。
清单 4. 设置和创建断点
<?php
function break-point(){
ob_flush();
flush();
sleep(.1);
debugBreak();
}
print("This will get shown first, ");
print("as will this<br>");
breakpoint();
print("This won't get shown until after ");
print("continuing the break-point<br>");
breakpoint();
print("END!");
?
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<span style="font-family:新宋体">breakpoint()</span> The function flushes buffered output and other buffered data to the web browser. The call to <span style="font-family:新宋体">sleep(.1)</span> is necessary so that the server has enough before the code terminates at <span style="font-family:新宋体">debugBreak()</span> Time refreshes the data to the Web browser. This function is an internal function of the PHP debugger extension downloaded earlier. Thus, calling <span style="font-family:新宋体">breakpoint()</span> will break the HTML block, <span style="font-family:新宋体">print()</span> and <span style="font-family:新宋体">echo()</span> The statement's data is flushed to the browser, and then code execution is aborted.
After you've written the code like in Listing 4, you can open a browser and point to test4.php, or you can view a PHP browser window (mine was http://localhost/debugArticle/test4.php). Each time a file is entered and saved, the debugging sequence is already started in the PHP browser window. If you are not using Windows, view test4.php through your browser. After saving the file, continue code execution with F8 or click Run > Resume. Keep doing this until the last line of output is <span style="font-family:新宋体">END!</span> (see Figures 9, 10, and 11).
Figure 9. Initial PHP browser output to the first breakpoint
Please note Figure 9 How to show execution as suspended in the Debug window.
Figure 10. PHP browser output after the first breakpoint and before the second breakpoint
The Debug window in Figure 10 still shows execution as pending, while the second set of data is displayed in the PHP browser.
Figure 11. Complete PHP browser output
Note that the code in the Debug window of Figure 11 does not Hang again and the entire script has been executed, as shown in Figure 11 for the PHP browser.
Now that you've seen the advantages of developing with PHPEclipse and the debugger extension, it's hard to imagine doing it without it.
Conclusion
Now that error reporting, print statements, PHPEclipse, and debugger extensions have been added to PHP's debugging technology set, you can reduce the number of lines of code by number of errors and become a more effective PHP coder. See Resources for some PHP tutorials on which you can test these new skills.
Download Sample code for PHP Debugging
References
Learn
You can refer to the English original text of this article on the developerWorks global site.
#Learn how to install Java on Windows and UNIX®-based systems.
Visit Eclipse.org for comprehensive information on programming and how to use it.
"Getting Started with the Eclipse Platform" (developerWorks, November 2002) provides a history and overview of Eclipse, including how to install Eclipse and Plugin details.
Visit PHPEclipse to learn more about installing PHPEclipse and how to use it.
DBG is a full-featured PHP debugger engine, an interactive tool that helps debug PHP scripts. Please read this tutorial at Installing and configuring the debugger.
To learn more about Eclipse, visit Eclipse project resources on developerWorks.
To learn more about PHP, visit developerWorks' PHP project resources.
#See the PHP manual for more information on error reporting.
Please read the instructions for installing PHP and Apache2 on Linux.
Please read the instructions for installing PHP and Apache2 on Windows.
For a series of developerWorks tutorials on learning PHP programming, see "Learn PHP, Part 1", Learn PHP, Part 2 and Learn PHP, Part 3.
Please pay close attention to developerWorks technical events and webcasts.
Visit developerWorks Open Source Zone Get rich how-to information, tools and project updates to help you use open source technology Develop and use them in IBM products.
Get products and technologies
Please start from PHP. net to download the latest version of PHP.
Please download the latest version of Apache 2.
#Please download Java Technology from Sun.
Please download the latest version of Eclipse from Eclipse.org.
Please download PHPEclipse from Sourceforge. Extract Eclipse to eclipse-install-dir, and then extract PHPEclipse to eclipse-install-dir. When installing the extension, follow the PHPEclipse instructions. However, comment out those lines where it is required to load and configure the PHP extension in the php.ini file. Uncomment these lines when you are ready to use the debugger.
Order the free SEK for Linux, this set of DVDs (two), including software from DB2®, Lotus®, Rational® , Tivoli® and WebSphere®, the latest IBM trial software for Linux.
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##About the author
##Tyler Anderson Graduated from Brigham Young University in 2004 with a degree in computer science. He is now in his final semester as a computer engineering master's student. In the past, he worked for DPMG.com as a database programmer, and now he is an engineer at Stexar Corporation in Beaverton, Ore.
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