Can you run the following on the shell:

export USE_ZEND_ALLOC=0
gdb --args /usr/local/bin/php -S localhost:8000 -t public -d zend_extension=/usr/local/Cellar/php/7.3.0/pecl/20180731/xdebug.so

Then on the (gdb) prompt type "run". Then request a web site on localhost:8000. When there is a crash in GDB (it should say segmentation fault), type "bt full", and attach that file.

This is the command output. I think it didn`t work properly.

gdb --args /usr/local/bin/php -S localhost:8000 -t public -d zend_extension=/usr/local/Cellar/php/7.3.0/pecl/20180731/xdebug.so

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BFD: /usr/local/Cellar/php/7.3.0/bin/php: unknown load command 0x32
BFD: /usr/local/Cellar/php/7.3.0/bin/php: unknown load command 0x32
"/usr/local/bin/php": not in executable format: file format not recognized
(gdb) run
Starting program: -S localhost:8000 -t public -d zend_extension=/usr/local/Cellar/php/7.3.0/pecl/20180731/xdebug.so
No executable file specified.
Use the "file" or "exec-file" command.
(gdb) bt full
No stack.
(gdb)

GDB doesn't seem to understand your binary. It seems to be related to some changes in OSX, so I'm not sure what I can do about that :-/

From what I googled, it's because it's not "codesigned" or whatever that is. There are instructions at https://stackoverflow.com/questions/52699661/macos-mojave-how-to-achieve-codesign-to-enable-debugging-gdb on how to fix that.

I am going to guess that this is the same issue as 0001583, but that is going to be a guess as no complete backtrace has been produced. Please try the upcoming 2.7.0RC1 release (out in the next few hours), and see if it solves the problem. If not, please reopen this issue, and attach a complete backtrace.