I am a big proponent of Xdebug and love PHPStorm. I have worked with many different setups for local environments and configuration seems to be a bit different each time.

My current environment is a docker container running on my local machine. I understand that PHPStorm is listening to 0.0.0.0, aka - to all network interfaces, and on a specified port (I'm using 9004). I also see that I can ping my local machine from the docker container hosting Xdebug.

What I don't understand is: when I put a breakpoint in PHPStorm, how does Xdebug know that it exists, so that when it hits that line of execution it should tell PHPStorm to stop?

CodePudding user response：

When Xdebug first connects to the IDE, the IDE sends over a list of breakpoints that it wants Xdebug to interrupt PHP at. If you have a look at a log file (made with xdebug.log=/tmp/xdebug.log), then you will see commands being send starting with breakpoint_set. There is then a type (-t), often line for a file/line breakpoint, as well as the file name and line number.

When PHP runs code, Xdebug intercepts the execution, and when it sees a match filename/line number combination, it pauses the execution and goes into command mode so that the IDE can send commands to inspect the current scope (by sending content_get) as well as further information about variables (with property_get). Then when you click "Continue" or "Step Over", the IDE sends a command to Xdebug to do the equivalent action.

To see a full description of the protocol, give the DBGp protocol specification a read.