Xdebug is a debugging and productivity extension for PHP

Xdebug and provides a range of features to improve the PHP development
experience.

Step Debugging
A way to step through your code in your IDE or editor while the script is
executing.

Improvements to PHP's error reporting
An improved var_dump() function, stack traces for Notices, Warnings, Errors
and Exceptions to highlight the code path to the error

Tracing
Writes every function call, with arguments and invocation location to disk.
Optionally also includes every variable assignment and return value for
each function.

Profiling
Allows you, with the help of visualisation tools, to analyse the
performance of your PHP application and find bottlenecks.

Code Coverage Analysis
To show which parts of your code base are executed when running unit tests
with PHP Unit.

= Fixed bugs:

- Fixed bug #725: EG(current_execute_data) is not checked in xdebug.c,
xdebug_statement_call.
- Fixed bug #723: xdebug is stricter than PHP regarding Exception property
types.
- Fixed bug #714: Cachegrind files have huge (wrong) numbers in some lines.
- Fixed bug #709: Xdebug doesn't understand E_USER_DEPRECATED.
- Fixed bug #698: Allow xdebug.remote_connect_back to be set in .htaccess.
- Fixed bug #690: Function traces are not appended to file with
xdebug_start_trace() and xdebug.trace_options=1.
- Fixed bug #623: Static properties of a class can be evaluated only with
difficulty.
- Fixed bug #614/#619: Viewing private variables in base classes through
the debugger.
- Fixed bug #609: Xdebug and SOAP extension's error handlers conflict.
- Fixed bug #606/#678/#688/#689/#704: crash after using eval on an
unparsable, or un-executable statement.
- Fixed bug #305: xdebug exception handler doesn't properly handle special
chars.

+ Changes:

- Changed xdebug_break() to hint to the statement execution trap instead of
breaking forcefully adding an extra stackframe.
- Prevent Xdebug 2.1.x to build with PHP 5.4.