This bug was originally marked as duplicate of bug 201450, that is already resolved. This bug is still valid, so this seems to be another bug, but it might be related.

Build: NetBeans IDE 8.0.2 (Build 201411181905)
VM: Java HotSpot(TM) 64-Bit Server VM, 23.6-b04, Java(TM) SE Runtime Environment, 1.7.0_11-b21
OS: Mac OS X

User Comments:
GUEST: Debugging a PHP project for the second time. 
1: Click Debug -> Debug Project in menu; 
2: Click Debug -> Finish Debugger Session in menu; 
3: Click Debug -> Debug Project

GUEST: Refreshing the web browser with XDebug connected.

GUEST: Using XDebug 
configured as http://wiki.netbeans.org/HowToConfigureXDebug#How_to_configure_XDebug
explains

karel_barel: pressed play button during debugging session

pchela.ilya: ?

GUEST: Started debugging.

Ujigami_Guy: Debugging php

pchela.ilya: ?

gt.hu: The Netbeans window was in the background for a while, then suddenly this error appeared.

GUEST: Just updated to beta 2, still getting a host of issues.

hubbitus: PHP debug session in progress

GUEST: just setup xdebug and ran for the first time correct.
Debug worked then immediately i got this error.

Configuration:
IIS7 on win7
pool: iis_iusr

GUEST: Went to a 404 page while in debug mode

GUEST: fds

padraigdoran: xdebug

GUEST: These errors come up a lot.

GUEST: 404 page while in debug mode

GUEST: ava.lang.IllegalArgumentException: Contents must be presorted - added value 244925 is less than preceding value 244981
	at org.netbeans.core.output2.IntList.add(IntList.java:76)
	at org.netbeans.core.output2.AbstractLines.addTabAt(AbstractLines.java:1122)
	at org.netbeans.core.output2.OutWriter.doWrite(OutWriter.java:452)
	at org.netbeans.core.output2.OutWriter.println(OutWriter.java:343)
	at org.netbeans.core.output2.NbWriter.println(NbWriter.java:165)
	at org.netbeans.modules.php.dbgp.packets.DbgpStream.process(DbgpStream.java:94)
	at org.netbeans.modules.php.dbgp.DebugSession.handleMessage(DebugSession.java:282)
	at org.netbeans.modules.php.dbgp.DebugSession.receiveData(DebugSession.java:268)
	at org.netbeans.modules.php.dbgp.DebugSession.receiveData(DebugSession.java:258)
[catch] at org.netbeans.modules.php.dbgp.DebugSession.run(DebugSession.java:145)
	at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
	at java.util.concurrent.FutureTask$Sync.innerRun(Unknown So

GUEST: cdebug debugging with remote server using ssh tunnel.

GUEST: Xdebugging

GUEST: System gets very slow due to processor usage of scanning process.

GUEST: Tried to work; PC gets rather slow due to scanning

tvollstaedt: Nothing, IDE was idle.

GUEST: Started debug session XDEBUG enabled

GUEST: Xdebugging

GUEST: after strting xdebug in php project

padraigdoran: xdebug

Ujigami_Guy: Debugging php

scriptoid: I was debugging a local web application when this error popped

Using xdebug and php 5.3 (thread safe)

karel_barel: remote debugging application with xdebug

GUEST: Debugging a PHP project

GUEST: added watch variable - since then I get this error.  Even when watch removed

GUEST: debug php code.  cakephp framwork form validators reject form submit  action

GUEST: debug php script

pchela.ilya: xdebug

karel_barel: clicked play button to continue debug session

GUEST: whilst debugg via the command line. It quits unexpectedly

GUEST: remote debugging in xdebug, ubuntu 12.04LTS, PHP 5.3

karel_barel: tried to debug code using xdebug

hte: was debugging a PHP site and noticed the error icon in bottom-right corner of Netbeans. Not sure what triggered this.

GUEST: started debugging applications

varloc2000: Work in browser - open rockmongo and bam!

GUEST: Refreshed page.

ywliu: I don't know why this exception was triggered. I just started my XDebug session for PHP and then I noticed this one.

GUEST: nao debuga

GUEST: Nothing, but it is a TYPO3 Project and there is the problem with different directories (links) pointing to the same source.  This problem makes it unpossible to work with Typo3 and Eclipse (if you have a big typo3 project)

GUEST: Refreshed the webpage while connected to XDebug.

karel_barel: refreshed page throwing an exception with running debug session

GUEST: Debugging

pchela.ilya: xdebug

GUEST: Xdebugging

GUEST: Xdebugging

GUEST: ditto

padraigdoran: xdebug

GUEST: sempre que ativo debug falha

GUEST: I get this error any time when starting the debugger
Installed the latest development version of netbeans
but still getting this error

pchela.ilya: ?

GUEST: cannot debug any file but the index.php file

karel_barel: debugging Nette project ending with exception,

Socket timeout happened before this one.

GUEST: Starting debugger.

GUEST: debug




Stacktrace: 
java.lang.IllegalArgumentException: Contents must be presorted - added value 3250159 is less than preceding value 3250172
   at org.netbeans.core.output2.IntList.add(IntList.java:76)
   at org.netbeans.core.output2.AbstractLines.addTabAt(AbstractLines.java:1300)
   at org.netbeans.core.output2.OutWriter.doWrite(OutWriter.java:481)
   at org.netbeans.core.output2.OutWriter.println(OutWriter.java:344)
   at org.netbeans.core.output2.NbWriter.println(NbWriter.java:165)
   at org.netbeans.modules.php.dbgp.packets.DbgpStream.process(DbgpStream.java:89)