Derick Rethans: The Mystery of the Missing Breakpoints

Derick Rethans has shared a post on his site with an experience he had with a mystery of missing breakpoints and some issues he commonly is asked about regarding Xdebug's breakpoint functionality.

Occasionally I see people mentioned that Xdebug does not stop at certain breakpoints. This tends to relate to multi-line if conditions, or if/else conditions without braces ({ and }).

f you set a breakpoint at either line 7, 11, or 12, you'll find that these are ignored. But why is that?

To help explain, he uses the vld tool to show the opcode behind the language's processing. In its results you can see that a EXT_STMT code is missing for the lines where the breakpoints were set. Xdebug doesn't see the marker it's expecting so the breakpoint isn't recognized and execution isn't halted as expected. He offers some suggestions you can use of other tools and functions to make sure the location you've selected can actually accommodate a breakpoint.