xdebug of different versions behaves differently when setting duplicate breakpoints.
xdebug version 2.5.5 allows you to set a duplicate breakpoint.
xdebug version 3.1.6 and higher does not allow setting a duplicate breakpoint by method.
Since version 3.2.0 it also does not allow setting a duplicate breakpoint by line.

If an attempt is made to set a duplicate breakpoint, xdebug returns an error:

<response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" command="breakpoint_set" transaction_id="141" state="enabled" status="starting" reason="ok">
	<error code="200">
		<message>
			<![CDATA[breakpoint could not be set]]>
		</message>
	</error>
</response>

This PR implements this error handling and marks the breakpoint as broken.
Tested on versions of xdebug: 2.5.5, 3.1.6, 3.2.1, 3.3.0.

Example for a line breakpoint:

• Write code

<?php

echo 'Hi';

$s = 12;

echo 'Hello';

• Put two breakpoints on the line echo 'Hello'; with different conditions (the order in which the breakpoints are set is important!):

  • first $s == 4
  • then $s == 12

• When debugging on xdebug version 2.5.5 or 3.1.6, it will stop at the point with the condition $s == 12.
  Everything is fine with this.

• When debugging on version 3.2.0, stopping at a point with the condition $s == 12 will not be executed, because the
  xdebug will not set the breakpoint. But the breakpoint is shown as normal, which is misleading.

Behavior before PR:

Behavior after PR: