PHP is one of the most widely used open-source server-side scripting languages that exist today. With over 20 million indexed domains using PHP, including major websites like Facebook, Digg and WordPress, there are good reasons why many Web developers prefer it to other server-side scripting languages, such as Python and Ruby.
Webgrind is an Xdebug profiling Web front end in PHP 5. It implements a subset of the features of kcachegrind, installs in seconds and works on all platforms. For quick ‘n’ dirty optimizations, it does the job.
Xdebug is one of the most popular debugging PHP extensions. It provides a ton of useful data to help you quickly find bugs in your source code. Xdebug plugs right into many of the most popular PHP applications, such as PHPEclipse and phpDesigner.
Gubed PHP Debugger
As the name implies, Gubed PHP Debugger is a PHP debugging tool for hunting down logic errors.
DBG is a robust and popular PHP debugger for use in local and remote PHP debugging. It plugs into numerous PHP IDE’s and can easily be used with the command line.
PHP_Debug is an open-source project that gives you useful information about your PHP code that can be used for debugging. It can output processing times of your PHP and SQL, check the performance of particular code blocks and get variable dumps in graphical form, which is great if you need a more visual output than the one given to you by print_r() or var_dump().
PHP_Dyn is another excellent PHP debugging tool that’s open-source. You can trace execution and get an output of the argument and return values of your functions.
MacGDBp is a live PHP debugger application for the Mac OS. It has all the features you’d expect from a fully featured debugger, such as the ability to step through your code and set breakpoints.