PHP Debugger

Every program no matter how well written can have bugs or other defects. Using a PHP Debugger will help find and eliminate unwanted software bugs from your PHP programs.

Using a PHP Debugger to Debug a PHP Script

For the beginner PHP developer, PHP debugging typically involves the use of print statements or logging of error messages from within in your PHP application code, for example, printing the value of different variables throughout different stages of the program execution.

This approach works in simple cases, but suffers from many drawbacks, for example:

  • It requires adding more code into your application, which takes time and might introduce even more bugs into your PHP script.
  • Debugging of PHP with print statements it's highly repetitive -- you'll need to keep printing out the value of different variables even if they don't change, and you'll have to clean up the mess afterwards.
  • Introduction of so many print statements and conditional can affect the performance of your PHP application.

A PHP Debugger provides a powerful way to simplify PHP debugging because it gives you complete visibility and control over the execution of PHP scripts and doesn't require that you make any changes to your PHP code. For example, using PhpED's PHP Debugger from NuSphere, you can perform various PHP debugging operations including:

  • Inspect any PHP variable or class
  • Change the value of a PHP variable
  • Set break points to interrupt PHP script execution
  • Make these break points act based on various conditions
  • Call a PHP function on the fly and inspect the results
  • Set break points dependant on Global True Expression
  • Jump to a different line of PHP code
  • Unwind the stack to see where an error originated
  • Support for remote PHP debugging
  • Enable secure debugging with SSH

You can download a free evaluation of PhpED's PHP Debugger so that you can follow along with the rest of this tutorial.

How to use the PhpED PHP Debugger

PhpED's PHP Debugger will let you step through your PHP code, control the program execution flow, watch the values of variables in the script as well as contents of the arrays and classes at each stage. You can even assign different values to the variables on the fly and do all of it without making any changes to your PHP application. In the following tutorial, you will learn how to use PhpED's PHP Debugger to find and eliminate bugs.

Step Through Lines of PHP Code

PhpED's PHP Debugger lets you step through the execution of PHP scripts, line-by-line, just as you would using a conventional software debugger. Using the PhpED Debugger toolbar, you can:

  • Step-In: Execute the following line of PHP code. If the next line of code is a function call, then begin execution at the beginning of the function.
  • Step-Out: Execute program execution until you reach the line of PHP code that called the currently executing function.
  • Step-Over: Execute the current line of PHP code

Single-Stepping through a PHP script using a PHP debugger is the easiest way to isolate bugs and is illustrated here:

Inspecting PHP Variables or Classes

PhpED's PHP Debugger provides three ways to see the values of PHP variables or the members of the PHP class.

  • The value of a variable is shown when the cursor is hovered over the variable in PHP code
  • The values of the Local variables and classes are displayed in Locals tab of PhpED debugger
  • The values of the Global variables and classes are displayed in Globals tab of PhpED debugger
  • Variables and classes added to the Watch tab of PhpED debugger and displayed there

The content of Locals, Globals and Watch tabs changes as you step through the code.

Assign a different value to PHP variables in the script

The PhpED PHP Debugger will even let you assign a different value to any PHP variable, so you can your fix before you change the actual PHP code in the script.

Set/toggle break points to interrupt PHP script execution

PhpED allows you to set and toggle breakpoints anywhere in your PHP code (illustrated below). The lines of code highlighted in blue represent breakpoints. The line in red shows the PHP script current state. You can set/toggle breakpoints from a toolbar, by typing the "F5" key, or by clicking on the red dot to the left of the line of code.

Call PHP function on the fly and inspect the results

Using the Immediate tab in the PhpED PHP debugger lets you can call any PHP function on the fly, even in the middle of the execution of your PHP script. Simply type in the function call in the window and press Enter. The functionality of immediate tab is illustrated below:

In this tutorial you learned about the different utilities to find and eliminate bugs from your PHP scripts using the PHP Debugger in NuSphere PhpED.

Next Steps:

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