[FIXED] Debug the PHP interpreter with GDB

Issue

I would like to use GDB to step though the C++ code that makes up the php.so Apache extension. I want to see what PHP is doing while it's running a PHP application. Preferably I would use an IDE like Netbeans or Eclipse on a LAMP system.

Solution

1. You want to get your hands on a debug build of mod_php (with symbols) or build your own (configure --enable-debug)
2. You should configure your Apache to always keep exactly one worker process instance up (which will be the instance you debug), that is, set MinSpareServers, MaxSpareServers and StartServers all to 1. Also make sure any timeout parameters are generously set
3. Use gdb or any graphical interface to gdb (such as ddd or Eclipse CDT) to attach to the one and only Apache worker process. Stick a breakpoint in one of the PHP sources etc. and continue.
4. Point your browser to your webserver and access a PHP page. Your breakpoint will trigger. If you want to wake the debugger at a particular point in your PHP script execution, generate a SIGTRAP from PHP and gdb will normally oblige you.

Have fun!

Answered By - vladr