Update README PHP setup with Xdebug

[shadydealer]

I went through the steps of installing xdebug and vdebug to debug my php setup and I couldn't, for the life of me get a debugger session working. I was getting the same error log over and over again:

[60807] Log opened at 2022-10-20 12:14:47.026666
[60807] [Step Debug] DEBUG: Found 'XDEBUG_CONFIG' ENV variable
[60807] [Step Debug] INFO: Connecting to configured address/port: 127.0.0.1:9000.
[60807] [Step Debug] INFO: Connected to debugging client: 127.0.0.1:9000 (through xdebug.client_host/xdebug.client_port). :-)
[60807] [Step Debug] -> <init xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" fileuri="{some_file_path}" language="PHP" xdebug:language_version="8.1.10" protocol_version="1.0" appid="60807" idekey="xdebug"><engine version="3.1.5"><![CDATA[Xdebug]]></engine><author><![CDATA[Derick Rethans]]></author><url><![CDATA[https://xdebug.org]]></url><copyright><![CDATA[Copyright (c) 2002-2022 by Derick Rethans]]></copyright></init>

[60807] [Step Debug] -> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" status="stopping" reason="ok"></response>

[60807] [Step Debug] WARN: 2022-10-20 12:14:47.028073: There was a problem sending 179 bytes on socket 6: Broken pipe.
[60807] Log closed at 2022-10-20 12:14:47.028225

There were 2 reasons:

1. The VdebugSetupPHP section includes a helper script to start a debugging session:

#!/bin/bash
export XDEBUG_CONFIG="idekey=xdebug"
/usr/bin/php "$@"

howerver, the xdebug docs also state that XDEBUG_SESSION=1 should be set, otherwise the debug session doesn't seem to start. So the php-xdebug script should be:

#!/bin/bash
export XDEBUG_SESSION=1
export XDEBUG_CONFIG="idekey=xdebug" # found out that this is not really needed
/usr/bin/php "$@"

2. The VdebugSetupPHP section says that we should set our host_port to 9000, but as stated here (I honestly don't understand the why, yet) that is wrong, and should be on a port different than 9000 (like 9003, the default xdebug port) and in the .vimrc we'd need to add the following lines:

let g:vdebug_options = {}
let g:vdebug_options["port"] = 9003 # same as port defined for xdebug

now, starting a debug session with php-xdebug works as expected :)

[letharion]

These are changes from xdebug 2 to 3, and the instructions haven't been updated yet.